335 research outputs found
On-chip, dynamic, cryogenic temperature monitoring via PDMS micro-bead coatings
No full textPolydimethylsiloxane (PDMS) microshells/beads coated onto an electrical current-carrying wire are demonstrated for on-chip, dynamic, cryogenic temperature measurement via monitoring optical whispering-gallery mode (WGM) frequency shifts. PDMS is found to be capable of supporting WGM resonance at cryogenic temperatures down to 95 K, limited by the present lab-built cryogenic working environment. The effect of the polymeric sensor diameter on temperature sensitivity is explored and discussed. The sensors are tested for their real-time temperature monitoring capabilities and accuracy in the cryogenic temperature regime of 95–140 K, and a comparison to a theoretical model, where the electrical resistivity of nichrome wire at cryogenic temperature is also experimentally determined, is examinedPeer reviewe
Whispering-gallery mode composite sensors for on-chip dynamic temperature monitoring
No full textWhispering-gallery mode temperature microsensors have been demonstrated to have extremely high accuracy. Previous experiments have been limited to indirect sensor heating by externally heating the local environment. In this paper, we coated PDMS films directly onto an electrical resistive wire as sensors, allowing on-chip dynamic temperature measurement. The effects of sensor size are discussed and verified through an expansion of the current theory of WGM resonance shifts to include composite materials. Finally, the WGM sensor’s measurements are compared to the same measurements recorded by a thermocouple, demonstrating the great advantages of WGM sensors for on-chip real temperature monitoring.Peer reviewe
Interview with Douglas Frenkel
No full textFor transcript, click the Download button above.
Douglas Frenkel (L\u2772), Morris Shuster Practice Professor of Law at Penn, is the architect of Penn Law’s nationally renowned clinical program, having served as Director of the Gittis Center for Clinical Legal Studies from 1980 to 2008. He specializes in alternative dispute resolution generally and mediation in particular. He is the author of innovative teaching materials and videotapes in this field and frequently serves as a mediator in employment, commercial, educational and family matters. Frenkel’s other major area of expertise is legal ethics, having been a founding faculty member of the Law School’s Center on Professionalism
First-order nematic-smectic phase transition for hard spherocylinders in the limit of infinite aspect ratio
No full textWe report Monte Carlo simulations of the nematic-smectic phase transition for a system of hard spherocylinders with infinite length-to-diameter ratio. A finite-size scaling analysis suggests that this system undergoes a first-order phase transition. When combined with other simulations of the phase behavior of spherocylinders, these results suggest that the nematic-smectic phase transition is first-order for all aspect ratios. This appears to rule out the possibility of a tricritical point predicted by several density-functional theories.PT: J; CR: BLADON P, 1996, J PHYS-CONDENS MAT, V8, P9445 BOLHUIS P, 1997, J CHEM PHYS, V106, P666 DOGIC Z, 1997, PHYS REV LETT, V78, P2417 FRENKEL D, 1988, J PHYS CHEM-US, V92, P3280 FRENKEL D, 1988, NATURE, V332, P882 HOSINO M, 1979, J PHYS SOC JPN, V46, P1709 MCGROTHER SC, 1996, J CHEM PHYS, V104, P6755 ONSAGER L, 1949, ANN NY ACAD SCI, V51, P627 PONIEWIERSKI A, 1990, PHYS REV A, V41, P6871 PONIEWIERSKI A, 1991, PHYS REV A, V43, P6837 PONIEWIERSKI A, 1992, PHYS REV A, V45, P5605 SOMOZA AM, 1990, PHYS REV A, V41, P965 TENWOLDE PR, 1996, J CHEM PHYS, V104, P9932 TKACHENKO AV, 1996, PHYS REV LETT, V77, P4218 TORRIE GM, 1974, CHEM PHYS LETT, V28, P578 VANDERSCHOOT P, 1996, J PHYS II, V6, P1557 VEERMAN JAC, 1990, PHYS REV A, V41, P3237; NR: 17; TC: 15; J9: PHYS REV E; PG: 4; GA: YM237Source type: Electronic(1
Numerical prediction of the melting curve of n-octane
No full textWe compute the melting curve of n-octane using Molecular Dynamics simulations with a realistic all-atom molecular model. Thermodynamic integration methods are used to calculate the free energy of the system in both the crystalline solid and isotropic liquid phases. The Gibbs-Duhem integration procedure is used to calculate the melting curve, starting with an initial point obtained from the free energy calculations. The calculations yield quantitatively accurate results: in the pressure range of 0-100 MPa, the calculated melting curve deviates by only 3 K from the experimental curve. This deviation falls just within the range of uncertainty of the calculations. (C) 1999 American Institute of Physics. [S0021-9606(99)52128-4].PT: J; CR: ANDERSEN HC, 1983, J COMPUT PHYS, V52, P24 BAEZ LA, 1995, MOL PHYS, V86, P385 BOLHUIS P, 1997, J CHEM PHYS, V106, P666 BOLHUIS PG, 1997, NATURE, V388, P235 CHEN B, 1998, J PHYS CHEM B, V102, P2578 FRENKEL D, 1984, J CHEM PHYS, V81, P3188 FRENKEL D, 1984, PHYS REV LETT, V52, P287 FRENKEL D, 1985, MOL PHYS, V55, P1171 FRENKEL D, 1992, J PHYS-CONDENS MAT, V4, P3053 HABENSCHUSS A, 1989, J CHEM PHYS, V91, P4299 KOFKE DA, 1993, J CHEM PHYS, V98, P4149 KOFKE DA, 1993, MOL PHYS, V78, P1331 KUCHTA B, 1992, PHYS REV B, V45, P5072 KUCHTA B, 1993, PHYS REV B, V47, P14691 KUCHTA B, 1995, J CHEM PHYS, V102, P3349 KUCHTA B, 1997, J CHEM PHYS, V106, P6771 LASO M, 1992, J CHEM PHYS, V97, P2817 MALANOSKI AP, 1997, J CHEM PHYS, V107, P6899 MALANOSKI AP, 1999, J CHEM PHYS, V110, P664 MARTIN MG, 1998, J PHYS CHEM B, V102, P2569 MARTYNA GJ, 1994, J CHEM PHYS, V101, P4177 MARTYNA GJ, 1996, MOL PHYS, V87, P1117 MATHISEN H, 1967, ACTA CHEM SCAND, V21, P9 MEIJER EJ, 1990, J CHEM PHYS, V92, P7570 MOOIJ GCA, 1992, J PHYS CONDENS MATT, V4, L255 NORMAN N, 1961, ACTA CHEM SCAND, V15, P1755 PANAGIOTOPOULOS AZ, 1987, MOL PHYS, V61, P813 PANAGIOTOPOULOS AZ, 1988, MOL PHYS, V63, P527 POLSON JM, UNPUB POLSON JM, 1998, J CHEM PHYS, V109, P318 RYCKAERT JP, 1977, J COMPUT PHYS, V23, P327 RYCKAERT JP, 1985, MOL PHYS, V55, P549 RYCKAERT JP, 1989, MOL PHYS, V67, P957 SCOTT RA, 1966, J CHEM PHYS, V44, P3054 SIEPMANN JI, 1990, MOL PHYS, V70, P1145 SIEPMANN JI, 1992, MOL PHYS, V75, P59 SIEPMANN JI, 1993, NATURE, V365, P330 SINGER SJ, 1990, J CHEM PHYS, V93, P1278 SMIT B, 1989, MOL PHYS, V68, P931 SMIT B, 1995, J CHEM PHYS, V102, P2126 SMITH GD, 1996, J PHYS CHEM-US, V100, P18718 SMITH JC, 1992, J AM CHEM SOC, V114, P801 TOBIAS DJ, 1997, J CHIM PHYS PCB, V94, P1482 TOXVAERD S, 1990, J CHEM PHYS, V93, P4290 TOXVAERD S, 1997, J CHEM PHYS, V107, P5197 TUCKERMAN M, 1992, J CHEM PHYS, V97, P1990 TUCKERMAN ME, 1990, J CHEM PHYS, V93, P1287 VEERMAN JAC, 1990, PHYS REV A, V41, P3237 VEGA C, 1992, J CHEM PHYS, V96, P9060 VEGA C, 1992, J CHEM PHYS, V97, P8543 WATANABE M, 1993, J CHEM PHYS, V99, P8063 WIDOM B, 1963, J CHEM PHYS, V39, P2808 WIDOM B, 1982, J PHYS CHEM-US, V86, P869 WILLIAMS DE, 1967, J CHEM PHYS, V47, P4680 WURFLINGER A, 1975, BER BUNSEN PHYS CHEM, V79, P1195; NR: 55; TC: 30; J9: J CHEM PHYS; PG: 10; GA: 215QQSource type: Electronic(1
Calculation of solid-fluid phase equilibria for systems of chain molecules
No full textWe study the first order solid-fluid phase transition of a system of semi-flexible Lennard-Jones chains using molecular dynamics simulations. Thermodynamic integration methods are used to calculate the free energy of the solid and fluid phases. The solid phase free energy per chain can be calculated to an accuracy of +/-0.03k(B)T with relative ease. The Gibbs-Duhem integration technique is used to trace out the complete melting curve, scarring with a single point on the curve obtained from the foe energy calculations. For the short chains studied here, we find that increasing the chain length stabilizes the solid phase; i.e., it raises the melting temperature at fixed pressure, and lowers the density at the transition at fixed temperature. Gibbs-Duhem integration was used also to investigate the effects of chain stiffness on the transition. We find that increasing the stiffness also acts to stabilize the solid phase. At fixed temperature, the transition is shifted to lower pressure and lower density with increasing chain stiffness. Further, we find that the density gap between solid and fluid broadens with increasing chain stiffness. (C) 1998 American Institute of Physics. [S0021-9606(98)50825-2].PT: J; CR: ANDERSEN HC, 1980, J CHEM PHYS, V72, P2384 BAEZ LA, 1995, MOL PHYS, V86, P385 BERENDSEN HJC, 1984, J CHEM PHYS, V81, P3684 BRUCE AD, 1997, PHYS REV LETT, V79, P3002 BULHUIS PG, 1997, J CHEM PHYS, V106, P666 BULHUIS PG, 1997, NATURE, V388, P235 ESCOBEDO FA, 1997, J CHEM PHYS, V106, P9858 FRENKEL D, 1984, J CHEM PHYS, V81, P3188 FRENKEL D, 1984, PHYS REV LETT, V52, P287 FRENKEL D, 1985, MOL PHYS, V55, P1171 FRENKEL D, 1991, J PHYS-CONDENS MAT, V3, P3053 FYNEWEVER H, 1998, J CHEM PHYS, V108, P1636 HOOVER WG, 1967, J CHEM PHYS, V47, P4873 HOOVER WG, 1985, PHYS REV A, V31, P1695 KOFKE DA, 1993, J CHEM PHYS, V98, P4149 KOFKE DA, 1993, MOL PHYS, V78, P1331 KUCHTA B, 1992, PHYS REV B, V45, P5072 KUCHTA B, 1993, PHYS REV B, V47, P14691 KUCHTA B, 1995, J CHEM PHYS, V102, P3349 KUCHTA B, 1997, J CHEM PHYS, V106, P6771 MARTYNA GJ, 1992, J CHEM PHYS, V97, P2635 MARTYNA GJ, 1996, MOL PHYS, V87, P1117 MEIJER EJ, 1990, J CHEM PHYS, V92, P7570 MOOIJ GCA, 1992, J PHYS CONDENS MATT, V4, L255 NOSE S, 1984, J CHEM PHYS, V81, P511 NOSE S, 1984, MOL PHYS, V52, P255 OGURA H, 1977, PROG THEOR PHYS, V58, P419 PANAGIOTOPOULOS AZ, 1987, MOL PHYS, V61, P813 PARRINELLO M, 1980, PHYS REV LETT, V45, P1196 ROSENBLUTH MN, 1955, J CHEM PHYS, V23, P356 SHENG YJ, 1994, MACROMOLECULES, V27, P400 SHENG YJ, 1996, MACROMOLECULES, V29, P4444 TUCKERMAN M, 1992, J CHEM PHYS, V97, P1990 TUCKERMAN ME, 1990, J CHEM PHYS, V93, P1287 VEERMAN JAC, 1990, PHYS REV A, V41, P3237 WIDOM B, 1963, J CHEM PHYS, V39, P2808 WIDOM B, 1982, J PHYS CHEM-US, V86, P869 WILSON MR, 1993, MOL PHYS, V80, P277 WILSON MR, 1994, MOL PHYS, V81, P675; NR: 39; TC: 26; J9: J CHEM PHYS; PG: 11; GA: 108FLSource type: Electronic(1
Wakimoto modules, opers and the center at the critical level
No full textAbstractWakimoto modules are representations of affine Kac–Moody algebras in Fock modules over infinite-dimensional Heisenberg algebras. In this paper, we present the construction of the Wakimoto modules from the point of view of the vertex algebra theory. We then use Wakimoto modules to identify the center of the completed universal enveloping algebra of an affine Kac–Moody algebra at the critical level with the algebra of functions on the space of opers for the Langlands dual group on the punctured disc, giving another proof of the theorem of B. Feigin and the author
Tipo de cambio real competitivo, inflación y política monetaria
No full textEditorial Review To analyze the sustainability of economic development models based on a “competitive” real exchange rate target is what leads R. Frenkel to reassess some macroeconomic policy dilemmas. Three key issues are stressed. In the first place, the author emphasizes the feasibility of conducting an active monetary policy, through a model that converges to a system of (strong) constraints that determine the “degrees of freedom” of monetary policy under this regime. Secondly, the author sets out the need for understanding the role of aggregate demand policies as offsetting (in an antiinflationary sense) the expansionary effects that exchange rate policy has on employment and economic activity. In this respect, the greater effectiveness of fiscal policy to attain such goal is finally remarked.Analizar la sustentabilidad de los modelos de desarrollo económico basados en un target de tipo de cambio real “competitivo” lleva a R. Frenkel a replantear en este artículo algunos dilemas de política macroeconómica. Se destacan tres ideas fuerza. En primer lugar, el autor rescata la viabilidad de mantener una política monetaria activa, a través de un modelo que concluye en un sistema de restricciones (fuertes) que determinan los “grados de libertad” de la política monetaria bajo este régimen. En segundo lugar, el autor plantea la necesidad de entender el rol de las políticas de demanda agregada en tanto compensadoras (antinflacionarias) de los efectos expansivos que la política cambiaria genera en la actividad y el empleo. En este sentido, se destaca finalmente la mayor efectividad de la política fiscal para lograr tal objetivo. 
The optimal pricing strategy for an insurer when risk preferences are stochastically distributed
No full textThe present paper analyzes the demand for insurance when the insurer has incomplete information about types of potential customers. We assume that customers´ risk preferences cannot be distinguished by the insurer. Therefore, the standard result in insurance economics that the insurer discriminates perfectly in prices cannot be applied. Instead, the present article examines the optimal pricing rule for an insurer faced with stochastic distribution of risk preferences. Within this general model framework, we show that an optimal strategy always exists. Both fixed and proportionate premium loadings (relative to expected loss) are considered. -- Der vorliegende Artikel analysiert die optimale Prämienpolitik eines Versicherers bei stochastischer Verteilung der Nachfragertypen auf Basis einer Preis-Absatz-Funktion. Dem Versicherer ist hier lediglich die Wahrscheinlichkeitsverteilung der individuellen Nachfragertypen bekannt und eine üblicherweise postulierte vollständige Preisdiskriminierung des Versicherers ist daher nicht möglich. Die allgemeine Preis-Absatz-Funktion des Versicherers variiert in Abhängigkeit der verwendeten Modellparameter. Wir zeigen, dass in diesem allgemeinen Modellrahmen stets eine optimale Preispolitik des Versicherers existiert. Dabei wird in Bezug auf den aktuariell fairen Wert der Police sowohl ein fixer als auch ein proportionaler Prämienzuschlag des Versicherers berücksichtigt.insurance demand,optimal insurance pricing,stochastically distributed risk preferences
Finite-size corrections to the free energies of crystalline solids
No full textWe analyze the finite-size corrections to the free energy of crystals with a fixed center of mass. When we explicitly correct for the leading (ln N/N) corrections, the remaining free energy is found to depend linearly on 1/N. Extrapolating to the thermodynamic limit (N → ∞), we estimate the free energy of a defect-free crystal of particles interacting through an r–12 potential. We also estimate the free energy of perfect hard-sphere crystal near coexistence: at ρσ3 = 1.0409, the excess free energy of a defect-free hard-sphere crystal is 5.918 89(4)kT per particle. This, however, is not the free energy of an equilibrium hard-sphere crystal. The presence of a finite concentration of vacancies results in a reduction of the free energy that is some two orders of magnitude larger than the present error estimate
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