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11.
Piotr Pawlowski 《Proceedings of the American Mathematical Society》1999,127(5):1493-1497
Let be a complex polynomial of degree having zeros in a disk . We deal with the problem of finding the smallest concentric disk containing zeros of . We obtain some estimates on the radius of this disk in general as well as in the special case, where zeros in are isolated from the other zeros of . We indicate an application to the root-finding algorithms.
12.
Supershell structure in alkali metal nanowires 总被引:1,自引:0,他引:1
Nanowires are formed by indenting and subsequently retracting two pieces of sodium metal. Their cross section gradually reduces upon retraction and the diameters can be obtained from the conductance. In previous work we have demonstrated that when one constructs a histogram of diameters from large numbers of indentation-retraction cycles such histograms show a periodic pattern of stable nanowire diameters due to shell structure in the conductance modes. Here, we report the observation of a modulation of this periodic pattern, in agreement with predictions of a supershell structure. 相似文献
13.
H. Gies J. Jaeckel J.M. Pawlowski C. Wetterich 《The European Physical Journal C - Particles and Fields》2007,49(4):997-1010
We investigate chiral symmetry breaking and color symmetry breaking in QCD. The effective potential of the corresponding scalar
condensates is discussed in the presence of non-perturbative contributions from the semiclassical one-instanton sector. We
concentrate on a color singlet scalar background which can describe chiral condensation, as well as a color octet scalar background
which can generate mass for the gluons. Whereas a non-vanishing singlet chiral field is favored by the instantons, we have
found no indication for a preference of color octet backgrounds. 相似文献
14.
Experimental investigation and analysis of heat transfer process between a gas-liquid spray flow and the row of smooth cylinders placed in the surface perpendicular to the flow has been performed. Among others, there was taken into account in the analysis the phenomenon of droplets bouncing and omitting the cylinder as well as the phenomenon of the evaporation process from the liquid film surface.In the experiments test cylinders were used, which were placed between two other cylinders standing in the row.From the experiments and the analysis the conclusion can be drawn that the heat transfer coefficients values for a row of the cylinders are higher than for a single cylinder placed in the gasliquid spray flow.
Nomenclature a distance between axes of cylinders, m - c l specific heat capacity of liquid, J/kg K - c g specific heat capacity of gas, J/kg K - D cylinder diameter, m - g l mass velocity of liquid, kg/m2s - ¯k average volume ratio of liquid entering film to amount of liquid directed at the cylinder in gas-liquid spray flow, dimensionless - k() local volume ratio of liquid entering film to amount of liquid directed at the cylinder in gas-liquid spray flow, dimensionless - L specific latent heat of vaporisation, J/kg - m mass fraction of water in gas-liquid spray flow, dimensionless - M constant in Eq. (9) - p pressure, Pa - p g statical pressure of gas, Pa - p w pressure of gas on the cylinder surface, Pa - p external pressure on the liquid film surface, Pa - r cylindrical coordinate, m - R radius of cylinder, m - T temperature, K, °C - T l, tl liquid temperature in the gas-liquid spray, K, °C - T w,tw temperature of cylinder surface, K, °C - T temperature of gas-liquid film interface, K - U liquid film velocity, m/s - w gas velocity on cylinder surface, m/s - w g gas velocity in free stream, m/s - W l liquid vapour mass ratio in free stream, dimensionless - W liquid vapour mass ratio at the edge of a liquid film, dimensionless - x coordinate, m - y coordinate, m - z complex variable, dimensionless - average heat transfer coefficient, W/m2K - local heat transfer coefficient, W/m2 K - average heat transfer coefficient between cylinder surface and gas, W/m2 K - g, local heat transfer coefficient between cylinder surface and gas, W/m2 K - mass transfer coefficient, kg/m2s - liquid film thickness, m - lg dynamic diffusion coefficient of liquid vapour in gas, kg/m s - pressure distribution function on a cylinder surface - function defined by Eq. (3) - l liquid dynamic viscosity, kg/m s - g gas dynamic viscosity, kg/m s - cylindrical coordinate, rad, deg - l thermal conductivity of liquid, W/m K - g thermal conductivity of gas, W/m K - mass transfer driving force, dimensionless - l density of liquid, kg/m3 - g density of gas, kg/m3 - w shear stress on the cylinder surface, N/m2 - w shear stress exerted by gas at the liquid film surface, N/m2 - air relative humidity, dimensionless - T -T w - w =T wTl Dimensionless parameters I= enhancement factor of heat transfer - m *=M l/Mg molar mass of liquid to the molar mass of gas ratio - Nu g= D/ g gas Nusselt number - Pr g=c g g/g gas Prandtl number - Pr l=clll liquid Prandtl number - ¯r=(r–R)/ dimensionless coordinate - Re g=wgD g/g gas Reynolds number - Re g,max=wg,max D g/g gas Reynolds number calculated for the maximal gas velocity between the cylinders - Sc=m * g/l–g Schmidt number =/R dimensionless film thickness 相似文献
Wärmeübergang an eine senkrecht anf eine Zylinderreihe auftreffende Gas-Flüssigkeits-Sprüh-Strömung
Zusammenfassung Es wurden Messungen und theoretische Analysen des Wärmeübergangs zwischen einer Gas-FlüssigkeitsSprüh-Strömung und den glatten Oberflächen einer Zylinderreihe durchgeführt, die senkrecht zum Sprühstrahl angeordnet waren. Dabei wurde in der Analyse unter anderem das Phänomen betrachtet, daß die Tropfen die Zylinderwand treffen und verfehlen können und daß sich ein Verdampfungsprozeß aus dem flüssigen Film an der Zylinderoberfläche einstellt.Gemessen wurde an einem zwischen zwei Randzylindern befindlichen Zylinder.Die Experimente und die Analyse gestatten die Schlußfolgerung, daß der Wärmeübergangskoeffizient für eine Zylinderreihe höher ist als für einen einzelnen Zylinder in der Sprühströmung.
Nomenclature a distance between axes of cylinders, m - c l specific heat capacity of liquid, J/kg K - c g specific heat capacity of gas, J/kg K - D cylinder diameter, m - g l mass velocity of liquid, kg/m2s - ¯k average volume ratio of liquid entering film to amount of liquid directed at the cylinder in gas-liquid spray flow, dimensionless - k() local volume ratio of liquid entering film to amount of liquid directed at the cylinder in gas-liquid spray flow, dimensionless - L specific latent heat of vaporisation, J/kg - m mass fraction of water in gas-liquid spray flow, dimensionless - M constant in Eq. (9) - p pressure, Pa - p g statical pressure of gas, Pa - p w pressure of gas on the cylinder surface, Pa - p external pressure on the liquid film surface, Pa - r cylindrical coordinate, m - R radius of cylinder, m - T temperature, K, °C - T l, tl liquid temperature in the gas-liquid spray, K, °C - T w,tw temperature of cylinder surface, K, °C - T temperature of gas-liquid film interface, K - U liquid film velocity, m/s - w gas velocity on cylinder surface, m/s - w g gas velocity in free stream, m/s - W l liquid vapour mass ratio in free stream, dimensionless - W liquid vapour mass ratio at the edge of a liquid film, dimensionless - x coordinate, m - y coordinate, m - z complex variable, dimensionless - average heat transfer coefficient, W/m2K - local heat transfer coefficient, W/m2 K - average heat transfer coefficient between cylinder surface and gas, W/m2 K - g, local heat transfer coefficient between cylinder surface and gas, W/m2 K - mass transfer coefficient, kg/m2s - liquid film thickness, m - lg dynamic diffusion coefficient of liquid vapour in gas, kg/m s - pressure distribution function on a cylinder surface - function defined by Eq. (3) - l liquid dynamic viscosity, kg/m s - g gas dynamic viscosity, kg/m s - cylindrical coordinate, rad, deg - l thermal conductivity of liquid, W/m K - g thermal conductivity of gas, W/m K - mass transfer driving force, dimensionless - l density of liquid, kg/m3 - g density of gas, kg/m3 - w shear stress on the cylinder surface, N/m2 - w shear stress exerted by gas at the liquid film surface, N/m2 - air relative humidity, dimensionless - T -T w - w =T wTl Dimensionless parameters I= enhancement factor of heat transfer - m *=M l/Mg molar mass of liquid to the molar mass of gas ratio - Nu g= D/ g gas Nusselt number - Pr g=c g g/g gas Prandtl number - Pr l=clll liquid Prandtl number - ¯r=(r–R)/ dimensionless coordinate - Re g=wgD g/g gas Reynolds number - Re g,max=wg,max D g/g gas Reynolds number calculated for the maximal gas velocity between the cylinders - Sc=m * g/l–g Schmidt number =/R dimensionless film thickness 相似文献
15.
Grothendieck polynomials, introduced by Lascoux and Schützenberger, are certain K-theory representatives for Schubert varieties. Symplectic Grothendieck polynomials, described more recently by Wyser and Yong, represent the K-theory classes of orbit closures for the complex symplectic group acting on the complete flag variety. We prove a transition formula for symplectic Grothendieck polynomials and study their stable limits. We show that each of the K-theoretic Schur P-functions of Ikeda and Naruse arises from a limiting procedure applied to symplectic Grothendieck polynomials representing certain “Grassmannian” orbit closures. 相似文献
16.
Anthony JM Garrett 《Contemporary Physics》2013,54(2):163-165
The dynamic electronic structure of atoms and molecules can be directly observed by means of the (e, 2e) reaction, which measures the distribution of energies and momenta of two electrons in coincidence after a knockout reaction initiated by an electron beam of known momentum incident on a molecular gas target. The molecular state for each event is identified by the electron separation energy. The recoil momentum for each event is known from the difference of measured initial and final momenta. It has been verified that values of this momentum are equal under suitable conditions to the momentum of the electron in the target immediately before knockout. Thus the spherically-averaged electron momentum distribution for each molecular orbital is measured. This is directly related to molecular orbitals calculated by the methods of quantum chemistry. Properties obtained by this method for different types of molecules are discussed. 相似文献
17.
J. Pawlowski 《Colloid and polymer science》1954,139(3):189
Ohne Zusammenfassung
The online version of the original article can be found at 相似文献
18.
Walter P. Pawlowski Richard D. Gilbert Raymond E. Fornes Suzanne T. Purrington 《Journal of Polymer Science.Polymer Physics》1988,26(5):1101-1110
The liquid-crystalline properties of three cellulose esters, phenylacetoxy cellulose (PAC), 4-methoxyphenylacetoxy cellulose (4MPAC), and p-tolylacetoxy cellulose (TAC) and two cellulose silyl ethers, trimethyl silyl cellulose (TMSC) and t-butyldimethylsilyl cellulose (TBDMSC), are reported. Hot-stage polarized light microscopy provided evidence regarding the formation of thermotropic mesophases in the PAC, 4MPAC, TAC, and TMSC in bulk form upon heating. The concomitant DSC data showed further evidence of the thermotropic nature of these materials. PAC, 4MPAC, TAC, and TMSC formed lyotropic mesophases at 44, 48, 50, and 27 wt%, respectively in CH2Cl2. The presence of fingerprint patterns in wholly anisotropic solutions in conjunction with optical rotation measurements confirmed the cholesteric nature of these liquid crystalline solutions. TBDMSC formed neither a lyotropic nor a thermotropic liquid-crystalline phase due to the low degree of substitution (DS 0.68) of this derivative. The hydroxyl substituents of PAC, 4MPAC, TAC, and TMSC may be readily removed under mild conditions to regenerate cellulose. 相似文献
19.
Cletus A D'Souza Vikramjit Chopra Richard Varhol Yuan-Yun Xie Slavita Bohacec Yongjun Zhao Lisa LC Lee Mikhail Bilenky Elodie Portales-Casamar An He Wyeth W Wasserman Daniel Goldowitz Marco A Marra Robert A Holt Elizabeth M Simpson Steven JM Jones 《BMC neuroscience》2008,9(1):1-14
Background
We have recorded responses from single neurons in murine visual cortex to determine the effectiveness of the input from the two murine cone photoreceptor mechanisms and whether there is any unique selectivity for cone inputs at this higher region of the visual system that would support the possibility of colour vision in mice. Each eye was stimulated by diffuse light, either 370 (strong stimulus for the ultra-violet (UV) cone opsin) or 505 nm (exclusively stimulating the middle wavelength sensitive (M) cone opsin), obtained from light emitting diodes (LEDs) in the presence of a strong adapting light that suppressed the responses of rods.Results
Single cells responded to these diffuse stimuli in all areas of striate cortex. Two types of responsive cells were encountered. One type (135/323 – 42%) had little to no spontaneous activity and responded at either the on and/or the off phase of the light stimulus with a few impulses often of relatively large amplitude. A second type (166/323 – 51%) had spontaneous activity and responded tonically to light stimuli with impulses often of small amplitude. Most of the cells responded similarly to both spectral stimuli. A few (18/323 – 6%) responded strongly or exclusively to one or the other spectral stimulus and rarely in a spectrally opponent manner.Conclusion
Most cells in murine striate cortex receive excitatory inputs from both UV- and M-cones. A small fraction shows either strong selectivity for one or the other cone mechanism and occasionally cone opponent responses. Cells that could underlie chromatic contrast detection are present but extremely rare in murine striate cortex. 相似文献20.