bluuebunny/crossref_metadata_2025 huggingface dataset:
Guanylyl cyclase and cGMP-specific phosphodiesterase participate in the acrosome reaction of starfish sperm
Authors: Kawase Osamu , Ueno Seiichi , Minakata Hiroyuki , Hoshi Motonori , Matsumoto Midori
Published: February 2005

In the starfish, Asterias amurensis, the cooperation of three components of the egg jelly, i.e. ARIS (acrosome reaction-inducing substance), Co-ARIS and asterosap, is responsible for inducing the acrosome reaction. Experimentally, ARIS and asterosap are sufficient for the induction. However, when sperm are treated only with asterosap, they become unresponsive to the egg jelly to undergo the reaction. In this study, we analysed the mechanism of the acrosome reaction, using sperm inactivation by asterosap as a clue. Asterosap causes a rapid and transient increase in intracellular cGMP through the activation of the asterosap receptor, a guanylyl cyclase, and causes an increase in intracellular Ca2+. When sperm were pretreated with asterosap, the guanylyl cyclase seemed to be inactivated irreversibly by dephosphorylation. They were still responsive to ARIS but no longer to asterosap. However, in the presence of IBMX or zaprinast, inhibitors against phosphodiesterases (PDEs), they retained their capacity to undergo the acrosome reaction in response to the egg jelly or ARIS alone. IBMX and zaprinast suppressed the intracellular catabolism of cGMP, but not of cAMP. These results suggest that guanylyl cyclase and cGMP-specific, IBMX- and zaprinast-susceptible PDEs are involved in the regulation of the acrosome reaction.
Viscoelectromagnetic coupling in precession‐nutation theory
Authors: Mathews P. M. , Guo J. Y.
Published: February 2005

The estimates made by Mathews et al. [2002] for the strengths of magnetic fields at the core mantle boundary and the inner core boundary were based on the not unreasonable hypothesis that the torques generated by differential wobbles between the fluid core on the one hand and the mantle and the inner core on the other are due to the magnetic fields crossing the core mantle and inner core boundaries. In this paper, we investigate the possibility that viscous drag at these boundaries might contribute significantly to the torques. Our objectives are to find out, first, whether it would become possible, with part of the torques accounted for by viscosity, to reduce the estimates for the magnetic field strengths at the two boundaries from the values obtained by Mathews et al. to the considerably lower values that had been favored earlier and, second, whether any bounds can be placed on the fluid viscosity itself. For this purpose, we have generalized the theory of Buffett et al. [2002] to obtain new expressions for the coupling constants representing the torques at the two boundaries which include the effects due to both electromagnetism and viscosity. With the use of these we find that Mathews et al.'s estimates for the coupling constants (which are independent of the mechanism of the coupling) place upper bounds on the viscosities at the core mantle and inner core boundaries. These bounds rule out not only the very high viscosity called for in recent literature relating to the translational oscillation modes of the inner core but also other earlier estimates, with the exception of those derived from theoretical and experimental studies on liquid metals. We find also that the magnetic field strength at the inner core boundary cannot be brought down to anywhere near the levels deduced from geodynamo theories unless the inner core ellipticity and/or the density jump at the inner core boundary are assigned values that appear unrealistic. Our theoretical formulation takes the variations of the unperturbed magnetic field and the ambient flow in the fluid core to be on spatial scales that are large compared to the kilometer‐scale thickness of the boundary layers which dominate the coupling of the fluid core to the mantle and the inner core at the tidal frequencies relevant to nutations. Possible variations on scales of a few kilometers or less are not taken into account. Such fine‐scale maps of the fields are not obtainable, at least at present, and so definitive computations are not possible. Our assessment, however, is that the effects of such small‐scale variations on the torques over the boundaries of the fluid core are unlikely to be large and that their impact on our conclusions is likely to be not significant.
Surface ventilation of the Black Sea's cold intermediate layer in the middle of the western gyre
Authors: Gregg M. C. , Yakushev E.
Published: February 2005

Understanding the origin of the shallow temperature minimum, known as the Cold Intermediate Layer (CIL), in the Black Sea has long been hampered by the scarcity of winter observations. During March 2003, we observed a cold‐air outbreak over the center of the Black Sea's Western Gyre. Freezing winds drove convection that cooled the surface mixed layer to 6.1°C and deepened it to 40 m, directly ventilating the upper 80% of the CIL, whose lower boundary was at 49 m. Concentrations of dissolved oxygen were 350 μM in the mixed layer and decreased rapidly to 70 μM at the base of the CIL, 9 m below the mixed layer. A few meters deeper, at the top of the Sub‐Oxic Layer (SOL), both oxygen and hydrogen sulfide became undetectable (<5 μM and <1 μM, respectively). Microstructure profiles revealed intermittent turbulence in the oxycline below the mixed layer. Average rates of turbulent dissipation were 10−9–10−8 W kg−1. The accompanying mixing produced diapycnal diffusivities, Kρ, that were only (1–4) × 10−6 m2 s−1. Consequently, turbulent fluxes were too weak to renew significantly either the lower 20% of the CIL or the SOL, whose top was 4 m below the bottom of the CIL and hence well‐removed from direct surface replenishment.
Seasonal and latitudinal variations of column averaged volume‐mixing ratios of atmospheric CO2
Authors: Warneke T. , Yang Z. , Olsen S. , Körner S. , Notholt J. , Toon G. C. , Velazco V. , Schulz A. , Schrems O.
Published: February 2005

Column‐averaged volume mixing ratios of CO2 have been obtained by ground based high‐resolution solar absorption spectrometry at Ny‐Alesund (Spitsbergen, 79°N) in 2002–2003 and during two ship cruises (54°N–34°S) on the Atlantic in 2003. Precisions are better than 0.4% at Ny‐Alesund and better than 0.6% for the cruises. The observed 11 ppmv (part per million by volume) seasonal amplitude of the CO2 column at Ny‐Alesund is about 5 ppmv smaller than surface in situ data and 2–4 ppmv greater than model‐predictions. The latitudinal gradient of column CO2 inferred from shipborne measurements is less than 2 ppmv in Oct/Nov 2003. During the cruise in Jan/Feb 2003 the observed latitudinal variation is about 7 ppmv. This strong variation is caused by pollution events (biomass burning) and natural variations. Low CO2 columns observed between 5°S–15°S are attributed to a strong seasonal amplitude of CO2 over Central Africa.
An attempt at improving a global spectral model by incorporating the second law of thermodynamics
Authors: Liu Chongjian , Liu Ying
Published: February 2005

A fluid such as the atmosphere is a many‐body system that has a vast amount of degrees of freedom in terms of statistical physics and thus obeys the second law of thermodynamics controlling the irreversible evolutionary direction of a many‐body system. This study shows that incorporating the thermodynamic irreversibility law into a hydrodynamic system leads to a noticeable improvement of a numerical weather prediction model. This is demonstrated by improved simulations from a set of numerical experiments using a global spectral model which incorporates the second law.
Has the Hadley cell been strengthening in recent decades?
Authors: Mitas Christos M. , Clement Amy
Published: February 2005

The intensity and structure of the Northern Hemisphere DJF Hadley cell as depicted in various commonly used data sets are examined. We find that the NCEP/NCAR and ECMWF reanalyses show a statistically significant intensification of their Hadley circulation throughout their periods. In marked contrast the NCEP‐DOE reanalysis does not show any discernible trend over its period. Furthermore, the Hadley cell structure differs substantially from the other two reanalyses. We also examine a data set of global rawinsonde observations in which the Hadley cell shows no intensification. Finally, we investigate the Hadley cell simulated by an atmospheric GCM. The ensemble mean shows a statistically significant intensification, though it is smaller in magnitude than the reanalyses. We conclude that the two major reanalyses appear to be in agreement on the strengthening of the Hadley cell in recent decades. However, discrepancies among data sets do raise questions about the robustness of this strengthening.
Recent trends in global ocean chlorophyll
Authors: Gregg Watson W. , Casey Nancy W. , McClain Charles R.
Published: February 2005

A 6‐year time series of remotely‐sensed global ocean chlorophyll was evaluated using linear regression analysis to assess recent trends. Global ocean chlorophyll has increased 4.1% (P < 0.05). Most of the increase has occurred in coastal regions, defined as bottom depth < 200 m, where an increase of 10.4% was observed. The main contributors to the increase were the Patagonian Shelf, Bering Sea, and the eastern Pacific, southwest African, and Somalian coasts. Although the global open ocean exhibited no significant change, 4 of the 5 mid‐ocean gyres (Atlantic and Pacific) showed declines in chlorophyll over the 6 years. In all but the North Atlantic gyre, these were associated with significant increases in sea surface temperature in at least one season. These results suggest that changes are occurring in the biology of the global oceans.
Comparative study of outer‐zone relativistic electrons observed by Akebono and CRRES
Authors: Seki Kanako , Miyoshi Yoshizumi , Summers Danny , Meredith Nigel P.
Published: February 2005

Simultaneous observations by CRRES and Akebono in the near‐ and off‐equatorial inner magnetosphere are used to examine the pitch angle dependence of the relativistic electron variation in the outer zone during the period from 24 August to 17 September 1990. This period includes two interesting time intervals, namely, a magnetic storm interval with a net reduction of outer‐zone electron flux and a nonstorm interval with a gradual increase of the relativistic electron population. The Akebono and CRRES data show the coherent behavior of the relativistic electron fluxes between the two satellites in the region 4 < L < 6, consistent with the “global coherence” of the outer‐zone variation suggested by previous multisatellite observations. On the other hand, the electron fluxes in the region 3 < L < 4, corresponding to the center of the outer zone after the magnetic storm from 26 August 1990, show a remarkable difference between near‐ and off‐equatorial electron fluxes: at L = 3.25, during the storm recovery phase, the flux increase lasts longer at Akebono (which measures small equatorial pitch angles) than at CRRES (which measures larger equatorial pitch angles), and after the storm, the decay of relativistic electron fluxes is faster for the latter than the former. The former longer‐lasting flux increase at Akebono than at CRRES is explicable with pitch angle evolution from a pancake‐like to a more isotropic pitch angle distribution with a timescale of a few days. The latter difference in the decay timescale after the storm is caused by the energy‐dependent electron loss, i.e., faster decay for lower‐energy electrons in the 1–2.5 MeV energy range. These results indicate that evolution of the pitch angle distribution can violate the “global coherence” of relativistic electron behavior at least in some cases, depending on the wave mode(s) responsible for the pitch angle diffusion of electrons, and suggest the importance of equatorial observations in the center of the outer zone.
Global ocean mean wave period data: Validation and description
Authors: Caires S. , Sterl A. , Gommenginger C. P.
Published: February 2005

A global comparison of altimeter and ERA‐40 mean wave period data is performed for the first time. Altimeter and ERA‐40 mean wave period are shown to compare well in non‐swell‐dominated conditions. Triply collocated altimeter, buoy, and ERA‐40 data show that the variance of the random errors is bigger for the ERA‐40 data and smaller for the buoy data. A new expression is given to relate altimeter data to wave period in wind‐dominated conditions. Provided this correction is applied, altimeter data are adequate for the most needed validation of global model mean wave period data in non‐swell‐dominated conditions. Triply collocated altimeter, buoy, and ERA‐40 also reveal that altimeter mean wave period is reliable even in swell conditions for moderate to high winds, in contrast to previous suggestions which limited its validity to wind‐dominated seas.
Origin of dimethylsulfide, non‐sea‐salt sulfate, and methanesulfonic acid in eastern Antarctica
Authors: Cosme E. , Hourdin F. , Genthon C. , Martinerie P.
Published: February 2005

Ignoring the origin of atmospheric chemicals is often a strong limitation to the full interpretation of their measurement. In this article, this question is addressed in the case of the sulfur species in Antarctica, with an original method of retrotransport of tracers. The retrotransport model is derived from the Laboratoire de Météorologie Dynamique Zoom‐Tracers (LMD‐ZT) atmospheric general circulation model, optimized for polar climate and expanded to simulate atmospheric sulfur chemistry. For two East Antarctic scientific stations (Dumont d'Urville and Vostok) the effects of transport and chemistry and the influence of oceanic, volcanic, and anthropogenic sources on dimethylsulfide (DMS), non‐sea‐salt (nss) sulfate, and methanesulfonic acid (MSA) concentrations are evaluated in summer and winter. The oceanic source largely dominates, but other sources can episodically be significant. The meridional origin and the age of DMS, MSA, and biogenic nss sulfate are also estimated. The latitudes of origin of MSA and nss sulfate are similar in summer, but they differ markedly in winter. This is a signature of their different chemical production scheme. Also, the interannual variability of the origin of the sulfur species at Vostok is weak compared to that at Dumont d'Urville. Acknowledging that the DMS concentrations in the ocean have no interannual variability in the model, this result suggests unsurprisingly that inland Antarctic stations may be better observation sites to monitor large‐scale DMS bioproductivity variability than coastal sites are. The combination of slower chemistry and more intense atmospheric circulation in winter leads to unexpected results, such as a younger DMS in winter than in summer at Vostok.
Role of sea ice in forcing the winter climate of Antarctica in a global climate model
Authors: Lachlan‐Cope Tom
Published: February 2005

Two different experiments have been conducted using the Hadley Centre's atmosphere‐only, global climate model to investigate the role of sea ice in forcing the Antarctic climate during the winter months. The first experiment, carried out by the Met Office Hadley Centre, involved forcing the model with observed sea ice concentration from the HadISST1 data set for the period 1870–1999 and showed that the observed temperature at Faraday/Vernadsky station (on the west coast of the Antarctic Peninsula) was well reproduced (correlation coefficient of 0.872) for the period 1973–1999, while at stations around the rest of the continent the observed temperature was not so highly correlated with the modeled temperature. The second experiment used two different yearly repeating sea ice concentrations, one being the average for the period 1975–1979 and the second the average for 1995–1999. The later period has generally less sea ice. This second experiment showed that the climate response to the sea ice forcing in the Amundsen Bellingshausen Sea was confined to the layers closest to the surface, while the response around the rest of Antarctica, where the katabatic wind flowing off the continent plays a role in the process, is over a much deeper layer of the atmosphere. It is also suggested that the katabatic flow may play a role in making the sea ice around East Antarctica insensitive to external climate forcing.
Characterization of airborne carbonate over a site near Asian dust source regions during spring 2002 and its climatic and environmental significance
Authors: Cao J. J. , Lee S. C. , Zhang X. Y. , Chow Judith C. , An Z. S. , Ho K. F. , Watson John G. , Fung Kochy , Wang Y. Q. , Shen Z. X.
Published: February 2005

During spring 2002, three dust storm events were monitored by filter sampling in Xi'an near an Asian dust source region of northwest China. The carbonate (CO32−) fraction was determined by sample acidification and thermal evolution. The CO32− accounted for 8.0 ± 0.8% of particles with aerodynamic diameter ≤2.5 μm (PM2.5) during dust storms and 4.7 ± 3.0% of PM2.5 between storms. The ratios of calcium to carbonate carbon were consistent with those of calcite (CaCO3). The δ13C and δ18O abundances in dust storm samples were −2.7 ± 0.7‰ and −5.8 ± 1.5‰, which differed from −8.3 ± 1.9‰ for δ13C and −10.8 ± 2.0‰ for δ18O during normal conditions. The δ13C is positively correlated with δ18O values (r = 0.78). This first measurement of isotopic abundance in Asian dust indicates the potential to quantify its contribution at distant locations using receptor models. By increasing the alkalinity of ocean water in the Pacific Ocean and buffering the atmospheric acidity of east Asia, the large amounts of airborne CO32− (as high as 44.8 Tg yr−1) entrained by Asian dust may provide an important atmospheric alkaline carbon reservoir for large‐scale climatic and environmental changes.
Nucleation studies in the Martian atmosphere
Authors: Määttänen A. , Vehkamäki H. , Lauri A. , Merikallio S. , Kauhanen J. , Savijärvi H. , Kulmala M.
Published: February 2005

We developed models for unary nucleation of water and carbon dioxide in the Martian atmosphere. Both homogeneous and heterogeneous nucleation on dust particles were studied. Our models are based on classical theory. We compare results of different adsorption approaches. Heterogeneous nucleation on the abundant dust particles seems to be the primary mechanism of both H2O and CO2 cloud formation in the Martian atmosphere. Heterogeneous nucleation is obtained at a saturation ratio of about 1.18 for H2O and 1.32 for CO2. Homogeneous nucleation is not likely to occur since it would require high supersaturations. We use our models to study nucleation as a function of height at different locations on Mars where ice fog or clouds have been observed. H2O ice nucleation results are in good agreement with surface fog observations and previous model studies. CO2 ice nucleation simulations in the polar hood cloud areas suggest that negative temperature perturbations caused by, e.g., adiabatic cooling in orographic waves or in convective plumes are required for the formation of CO2 clouds.
Limited range of interspecific vital effects in coccolith stable isotopic records during the Paleocene‐Eocene thermal maximum
Authors: Stoll Heather M.
Published: February 2005

Small but significant differences exist among stable carbon and oxygen isotopic excursions measured in coccolith‐dominated bulk carbonate and planktic foraminifera during the Paleocene‐Eocene thermal maximum (PETM). One hypothesis suggests that the bulk carbonate isotopic record is compromised by changing nannofossil assemblages, since modern nannofossils show a large (5 permil) range of interspecific vital effects. New techniques are employed here to separate different size fractions of coccoliths from PETM sediments at ODP Site 690 for isotopic analysis, removing a major portion of the variation in nannofossil assemblages. Isotopic compositions of coarse and fine coccolith fractions dominated by coccoliths of genus Chiasmolithus and Toweius, respectively, differ by less than 0.5 permil for both oxygen and carbon. The near‐monogeneric Toweius record closely parallels the main trends in the bulk carbonate isotope records, including multiple steps in the negative carbon isotopic excursion, suggesting that the trends in the bulk carbonate record are not artifacts of changing species assemblages. Because both coccolithophorids and symbiont‐bearing foraminifera like Acarinina must inhabit the photic zone, it is unlikely that the 103 year lags in isotope event onset between coccoliths and Acarinina reflect true time‐transgressive invasion of isotopically depleted CO2 into the water column. The small range of vital effects among Paleocene coccoliths is unlikely to result from diagenetic homogenization, and instead may reflect more similar carbon acquisition strategies of Paleocene coccolithophorid algae due to larger and/or more similar cell sizes and higher atmospheric carbon dioxide. The small range of vital effects suggests that bulk carbonate records are likely reliable for other early and pre‐Cenozoic sediments where foraminifera are often scarce.
A small hemispherical helical antenna array for two‐dimensional GPS beam‐forming
Authors: Hui H. T. , Aditya S. , Mohamed F. Bin S. , Hafiedz‐Ul A. Bin T.
Published: February 2005

A small hemispherical helical antenna array with multibeam output for GPS beam‐forming is designed and characterized. A Butler matrix beam‐forming network is designed to provide four spatial beams in a two‐dimensional directional space. The original design of the hemispherical helical antenna elements is modified in order to match it to the system impedance. Our study shows that even after an ∼30° scan from the normal direction, the maximum change in beam width is only 6°, the maximum change in axial ratio is 1.4 dB, and the maximum change in power gain is 1.1 dB. These characteristics indicate that the array can be potentially used for GPS beam‐forming.
Exact analytic solutions of nonlinear boundary value problems in fluid mechanics (Blasius equations)
Authors: Panayotounakos D. E. , Sotiropoulos N. B. , Sotiropoulou A. B. , Panayotounakou N. D.
Published: February 2005

In this work it is shown that, by a series of admissible functional transformations, the generalized Blasius equation in fluids can be exactly reduced to a three-term generalized Emden–Fowler equation. Furthermore, the restricted in axisymmetric flows and simplified forms of this equation can be reduced to (i) two-term generalized Emden–Fowler equations; (ii) generalized Emden–Fowler equations; (iii) Emden–Fowler equations of the normal form; and (iv) Abel equations of the second kind. By means of a recently developed mathematical solution methodology (Panayotounakos, Fifth Greek Congress on Mechanics, Xania, Crete, 22–25 June 2004, Hellas, Greece), we provide exact analytic solutions for the simplified as well as for the restricted forms of the above-mentioned Blasius equations. Thus, it is proved that important, unsolvable in exact form problems in nonlinear fluid dynamics now can be analytically solved.
The NaK 1(b)ΠΩ=3 state hyperfine structure and the 1(b)ΠΩ=3∼2(A)Σ+1 spin–orbit interaction
Authors: Burns P. , Wilkins A. D. , Hickman A. P. , Huennekens J.
Published: February 2005

We have measured the hyperfine structure of mutually perturbing rovibrational levels of the 1(b)Π03 and 2(A)Σ+1 states of the NaK molecule, using the perturbation-facilitated optical-optical double resonance method with copropagating lasers. The unperturbed 1(b)Π03 levels are split into four hyperfine components by the Fermi contact interaction bFI∙S. Mixing between the 1(b)Π03 and 2(A)Σ+1 levels imparts hyperfine structure to the nominally singlet component of the perturbed levels and reduces the hyperfine splitting of the nominally triplet component. Theoretical analysis relates these observations to the hyperfine splitting that each 1(b)Π03 level would have if it were not perturbed by a 2(A)Σ+1 level. Using this analysis, we demonstrate that significant hyperfine splitting arises because the 1(b)Π03 state cannot be described as pure Hund’s case (a). We determine bF for the 1(b)Π03 levels and also a more accurate value for the magnitude of the singlet-triplet spin–orbit coupling HSO=⟨1(b)Π03(vb,J)∣HSO∣2(A)Σ+1(vA,J)⟩. Using the known spectroscopic constants of the 1(b)Π3 state, we obtain bF=0.00989±0.00027cm−1. The values of ∣HSO∣ are found to be between 2 and 3cm−1, depending on vb, vA, and J. Dividing ∣HSO∣ by calculated vibrational overlap integrals, and taking account of the 1(b)ΠΩ3 rotational mixing, we can determine the magnitude of the electronic part Hel of HSO. Our results yield ∣Hel∣=(16.33±0.15)cm−1, consistent with our previous determinations using different techniques.
Adaptive importance sampling Monte Carlo simulation of rare transition events
Authors: de Koning Maurice , Cai Wei , Sadigh Babak , Oppelstrup Tomas , Kalos Malvin H. , Bulatov Vasily V.
Published: February 2005

We develop a general theoretical framework for the recently proposed importance sampling method for enhancing the efficiency of rare-event simulations [W. Cai, M. H. Kalos, M. de Koning, and V. V. Bulatov, Phys. Rev. E 66, 046703 (2002)], and discuss practical aspects of its application. We define the success/fail ensemble of all possible successful and failed transition paths of any duration and demonstrate that in this formulation the rare-event problem can be interpreted as a “hit-or-miss” Monte Carlo quadrature calculation of a path integral. The fact that the integrand contributes significantly only for a very tiny fraction of all possible paths then naturally leads to a “standard” importance sampling approach to Monte Carlo (MC) quadrature and the existence of an optimal importance function. In addition to showing that the approach is general and expected to be applicable beyond the realm of Markovian path simulations, for which the method was originally proposed, the formulation reveals a conceptual analogy with the variational MC (VMC) method. The search for the optimal importance function in the former is analogous to finding the ground-state wave function in the latter. In two model problems we discuss practical aspects of finding a suitable approximation for the optimal importance function. For this purpose we follow the strategy that is typically adopted in VMC calculations: the selection of a trial functional form for the optimal importance function, followed by the optimization of its adjustable parameters. The latter is accomplished by means of an adaptive optimization procedure based on a combination of steepest-descent and genetic algorithms.
Compact and efficient basis sets of s- and p-block elements for model core potential method
Authors: Miyoshi Eisaku , Mori Hirotoshi , Hirayama Ryo , Osanai You , Noro Takeshi , Honda Hiroaki , Klobukowski Mariusz
Published: February 2005

We propose compact and efficient valence-function sets for s- and p-block elements from Li to Rn to appropriately describe valence correlation in model core potential (MCP) calculations. The basis sets are generated by a combination of split MCP valence orbitals and correlating contracted Gaussian-type functions in a segmented form. We provide three types of basis sets. They are referred to as MCP-dzp, MCP-tzp, and MCP-qzp, since they have the quality comparable with all-electron correlation consistent basis sets, cc-pVDZ, cc-pVTZ, and cc-pVQZ, respectively, for lighter atoms. MCP calculations with the present basis sets give atomic correlation energies in good agreement with all-electron calculations. The present MCP basis sets systematically improve physical properties in atomic and molecular systems in a series of MCP-dzp, MCP-tzp, and MCP-qzp. Ionization potentials and electron affinities of halogen atoms as well as molecular spectroscopic constants calculated by the best MCP set are in good agreement with experimental values.
SO(10) group theory for the unified model building
Authors: Fukuyama Takeshi , Ilakovac Amon , Kikuchi Tatsuru , Meljanac Stjepan , Okada Nobuchika
Published: February 2005

The complete tables of Clebsch–Gordan (CG) coefficients for a wide class of SO(10) SUSY grand unified theories (GUTs) are given. Explicit expressions of states of all corresponding multiplets under standard model gauge group G321=SU(3)C×SU(2)L×U(1)Y, necessary for evaluation of the CG coefficients are presented. The SUSY SO(10) GUT model considered here includes most of the Higgs irreducible representations usually used in the literature, 10, 45, 54, 120, 126, 126¯, and 210. Mass matrices of all G321 multiplets are found for the most general superpotential. These results are indispensable for the precision calculations of the gauge couplings unification and proton decay, etc.
Shear viscoelasticity of ultrasonic couplers by broadband reflectivity measurements
Authors: Yoneda A. , Ichihara M.
Published: February 2005

The acoustic shear wave velocity and attenuation of ultrasonic couplers were investigated by broadband reflectivity measurements at around room temperature and 15–30 MHz. The feature of the present technique is to use impulsive pulse and normal incident waves against a reflective interface. Its characteristics are compared with the inclined incident wave technique used so far. It is found that the normal incident wave technique is nearly free from the effects of diffraction in contrast with the inclined incident wave technique. In the present work, the acoustic shear properties and their temperature dependence were investigated for nine commercial couplers at 15, 25, and 35 °C. The shear wave velocity dispersion was clearly observed in every measurement in the investigated frequency range; these data are useful for design in ultrasonic shear wave experiments. Furthermore, a linear relationship was found between the rigidity and Q value for hydroxyl carbons and naphten oils. The difference in the physical properties can be attributed to differences in the chemical properties of the samples. Therefore, the present technique is useful for investigating both the macroscopic and microscopic properties of viscoelastic materials.
Theoretical study of the photoinduced transfer among the ground state and two metastable states in [Fe(CN)5NO]2−
Authors: Ishikawa Takeshi , Tanaka Kiyoshi
Published: February 2005

Ab initio calculations were performed to investigate photoinduced transfers among the ground state (GS) and two metastable states (MS1 and MS2) of [Fe(CN)5NO]2−. We obtained the global potential energy surface of the electronic ground state by a scheme of multireference singly and doubly excited configuration interaction followed by a Davidson-type quadruple correction (MRSDCI+Q). The ground state surface has three local minima corresponding to GS, MS1, and MS2. The character of bond between Fe and the nitrosyl group are discussed. We carried out calculations of the lower five electronic excited states by MRSDCI+Q. The main configurations of these lower five excited states were represented by the dFe→πNO* transition accompanied by considerable back-donation. The potential energy surfaces of the six states, including the ground state, were obtained by state averaged complete active space self-consistent field calculations. The surfaces have several conical intersections and avoided crossings in the reaction pathway. The photoinduced transfers among GS, MS1, and MS2 are caused by the nonadiabatic effect near these crossings.
Spectroscopic ellipsometric study on dispersion of optical constants of Gd2O3 films
Authors: Bhattacharyya D. , Biswas A.
Published: February 2005

Electron-beam evaporated Gd2O3 films have been characterized by spectroscopic ellipsometry technique. The experimental ellipsometric data have been fitted with theoretical models to derive information on the sample structure and dispersion of the optical constants of bulk Gd2O3. Three different dispersion models, proposed so far for amorphous materials have been used for the calculation of the refractive-index dispersion and results obtained from these models have been compared.
Electrical resistance of low-angle tilt grain boundaries in acceptor-doped SrTiO3 as a function of misorientation angle
Authors: De Souza Roger A. , Fleig Jürgen , Maier Joachim , Zhang Zaoli , Sigle Wilfried , Rühle Manfred
Published: February 2005

The transport of charge across symmetrical low-angle [001] tilt grain boundaries in Fe-doped SrTiO3 was examined. Grain boundary resistances were obtained from impedance spectroscopy measurements on bicrystals with misorientation angles θ=2.3°, 5.4°, and 7.8° as a function of temperature and oxygen partial pressure. By comparing these data with values predicted from a double Schottky-barrier model, we show that the resistance of a low-angle tilt grain boundary in acceptor-doped SrTiO3 is correlated with its dislocation content, but in a nontrivial manner.
High pretilt four-domain twisted nematic liquid crystal display by microrubbing: Process, characterization, and optical simulation
Authors: Varghese Soney , Crawford Gregory P. , Bastiaansen Cees W. M. , de Boer Dick K. G. , Broer Dirk J.
Published: February 2005

A microrubbing (μ-rubbing) technique was utilized to create four-domain alignment in a liquid crystal display sample. A small metallic sphere under sufficient load was used to directly rub a homeotropic polyimide alignment layer to create a large surface pretilt angle. We demonstrate a 47-μm linewidth and a variable pretilt angle with respect to the substrate plane for different loads. The homeotropic polyimide surface was μ rubbed in such a way that neighboring alignment regions are rubbed in opposite directions. liquid crystal cells were constructed with two μ-rubbed substrates where the rubbing directions are orthogonal to each other. With this cell configuration we obtained four domains consisting of two left-handed and two right-handed twisted nematic subpixels. We report on the electro-optic performance properties, viewing angle characteristics, the relationship between pretilt angle versus load, and thermal aging study of the four-domain liquid crystal cell. The optical simulations of the liquid crystal director orientation, viewing angle characteristics, and the contrast ratio of the four domains are also presented. The experimental results are in agreement with the simulation results.
Time-resolved observation of the change of electrode shape in single discharge: Rapid self-forming of a thin electrode
Authors: Tanabe Rie , Ito Yoshiro , Takezawa Hideki , Mohri Naotake
Published: February 2005

A very thin, needlelike electrode can be formed at the tip of thin tungsten electrode by a single discharge with rather high discharge current. We have demonstrated some practical applicability of such very thin electrode. Understanding the formation mechanism of such electrodes is an important issue to utilize the phenomenon to practical applications. We should see what happens on the electrode during the discharge. In this study, the change of electrode shape at tip part of a thin metal electrode induced by single discharge with a large current was observed dynamically by a stroboscopic imaging system with high time resolution. In the imaging system, the second harmonics of a Q-switched neodyum: yttrium-aluminum-garnet laser is used for lighting of charge-coupled device camera and it can take a photo with time resolution of about 10ns. Electrode materials were tungsten and copper of 100μm diameter and the discharge current was 30A with 400μs duration. Both the positive and negative polarities of electrodes in machining oil as well as in air were examined using steel work piece. Rather drastic move of melt formed by the discharge occurred after discharge in all cases. Observed images reveal that the electrode tip part after single discharge is in a molten state and the melt part moves upwards after the end of the discharge, and final electrode shape is formed at about 1ms after the discharge. The thin, needlelike form of tungsten electrode is found to be the residue of unmelted portion of the electrode left after the move of melted part. Tungsten electrode becomes the needlelike shape when the thin electrode has negative polarity. When the polarity is reversed, or copper electrodes are used, the tips of the electrodes become spherical forms. For copper electrode with negative polarity in air and at some specific time, droplets of molten metal are suspended in the space between the electrode and the work piece.
Single-charge devices with ultrasmall Nb∕AlOx∕Nb trilayer Josephson junctions
Authors: Dolata R. , Scherer H. , Zorin A. B. , Niemeyer J.
Published: February 2005

Josephson junction transistors and 50-junction arrays with linear junction dimensions from 200nm down to 70nm were fabricated from standard Nb∕AlOx∕Nb trilayers. The fabrication process includes electron beam lithography, dry etching, anodization, and planarization by chemical-mechanical polishing. The samples were characterized at temperatures down to 25mK. In general, all junctions are of high quality and their I-U characteristics show low leakage currents and high superconducting energy gap values of Δ≈1.35meV. The characteristics of the transistors and arrays exhibit some features in the subgap area, associated with tunneling of Cooper pairs, quasiparticles, and their combinations due to the redistribution of the bias voltage between the junctions. Total island capacitances of the transistor samples ranged from 1.5fF to 4fF, depending on the junction sizes. Devices made of junctions with linear dimensions below 100nm×100nm demonstrate a remarkable single-electron behavior in both superconducting and normal state. We also investigated the area dependence of the junction capacitances for transistor and array samples.
Electrical modification in Cu(In,Ga)Se2 thin films by chemical bath deposition process of CdS films
Authors: Jiang C.-S. , Noufi R. , Ramanathan K. , Moutinho H. R. , Al-Jassim M. M.
Published: February 2005

We have measured the two-dimensional electrical potential distribution on the surface of photovoltaic Cu(In,Ga)Se2 (CIGS) thin films using the nanoscale electrical characterization of scanning Kelvin probe microscopy. The potential peak on the grain boundaries becomes sharper after the sample is rinsed in high-purity water, and the height of the potential peak becomes smaller after chemical treatments in a solution similar to that used in the chemical bath deposition of CdS films. This demonstrates an effect of surface Na removal by the water rinsing and downward band bending on the CIGS film surface induced by the chemical treatment. This electrical modification is expected to benefit the properties of the electrical junction and, hence, CIGS/CdS device performance.
Correlation between particle removal and shock-wave dynamics in the laser shock cleaning process
Authors: Lim Hyunkyu , Jang Deoksuk , Kim Dongsik , Lee Jin Won , Lee Jong-Myoung
Published: February 2005

It has been shown that the laser shock cleaning (LSC) method is effective for eliminating micron- and submicron-scale particulates from solid surfaces. In the LSC process, a high-power laser pulse induces optical breakdown of the ambient gas close to the solid surface to be cleaned and the subsequently-created shock wave followed by a high-speed flow stream detaches the particles. Therefore, there should be a strong correlation between the dynamics of the shock wave and the cleaning performance. In this work, experimental analyses are conducted to measure the cleaning performance using micron-sized alumina particles attached to a silicon surface. The experimental data showing the particle-removal performance are compared with the results of the dynamics of the laser-induced shock waves, leading to a simple model for particle removal by the LSC scheme in the continuum-flow regime.
Dielectric relaxation and tunability of Bi2O3–ZnO–CaO–Ta2O5 ceramics
Authors: Shen Bo , Zhai Jiwei , Yao Xi
Published: February 2005

( Bi 2 − x Ca x ) ( Zn 1 ∕ 3 Ta 2 ∕ 3 ) 2 O 7  (0⩽x⩽1) ceramic were prepared by using a solid-state reaction technique. (Bi1.2Ca0.8)(Zn1∕3Ta2∕3)2O7 was found to have cubic pyrochlore structure, while (Bi1.9Ca0.1)(Zn1∕3Ta2∕3)2O7 was shown to have a monoclinic zirconolite structures. cubic pyrochlore (Bi1.2Ca0.8)(Zn1∕3Ta2∕3)2O7, not monoclinic zirconolite (Bi1.9Ca0.1)(Zn1∕3Ta2∕3)2O7, was found to show relaxation behavior at room temperature. Dielectric constant and dielectric loss were measured as functions of electric field and temperature. The results show a maximum tunability of 12% under a bias 60 KV∕cm in cubic-pyrochlore-structure (Bi1.2Ca0.8)(Zn1∕3Ta2∕3)2O7 ceramics.
Laser excitation of NaNe collision pairs probing the AΠ2 potential
Authors: Grimpe A. , Grosser J. , Hoffmann O. , Rebentrost F.
Published: February 2005

Experimental differential cross sections for the collision process Na(3s)S2+Ne+hν→Na(3p)P2+Ne are reported. By comparison with calculated cross sections, we are able to discriminate between different spectroscopic and quantum chemical AΠ2 potentials with cm−1 sensitivity.
The effect of antimony in the growth of indium arsenide quantum dots in gallium arsenide (001)
Authors: Sun Y. , Cheng S. F. , Chen G. , Hicks R. F. , Cederberg J. G. , Biefeld R. M.
Published: February 2005

The effect of an initial saturation coverage of antimony on the growth of indium arsenide quantum dots on gallium arsenide has been studied during metalorganic vapor-phase epitaxy. After depositing one to two bilayers of InAs at 723 K, the samples were quenched, transferred to ultrahigh vacuum, and characterized by scanning tunneling microscopy and x-ray photoelectron spectroscopy. It has been found that the critical thickness for onset of quantum dot formation is 33% less with Sb present as compared to without Sb. The antimony incorporates into the quantum dots, increasing their density and total volume, and causing them to be more densely clustered together.
Experimental demonstration of fiber-accessible metal nanoparticle plasmon waveguides for planar energy guiding and sensing
Authors: Maier Stefan A. , Friedman Michelle D. , Barclay Paul E. , Painter Oskar
Published: February 2005

Experimental evidence of mode-selective evanescent power coupling at telecommunication frequencies with efficiencies up to 75% from a tapered optical fiber to a metal nanoparticle plasmon waveguide is presented. The waveguide consists of a two-dimensional square lattice of lithographically defined Au nanoparticles on an optically thin silicon membrane. The dispersion and attenuation properties of the waveguide are analyzed using the fiber taper. The high efficiency of power transfer into these waveguides solves the coupling problem between conventional optics and plasmonic devices and could lead to the development of highly efficient plasmonic sensors and optical switches.
Monitoring of living cell attachment and spreading using reverse symmetry waveguide sensing
Authors: Horvath Robert , Pedersen Henrik C. , Skivesen Nina , Selmeczi David , Larsen Niels B.
Published: February 2005

The effect of the attachment and spreading of living cells on the modes of a grating coupled reverse symmetry waveguide sensor is investigated in real time. The reverse symmetry design has an increased probing depth into the sample making it well suited for the monitoring of cell morphology. As a result, significant changes in the incoupling peak height and peak shape were observed during cell attachment and spreading. It is suggested that the area under the incoupling peaks reflects the initial cell attachment process, while the mean peak position is mostly governed by the spreading of the cells.
Predicted properties of microhollow cathode discharges in xenon
Authors: Boeuf J. P. , Pitchford L. C. , Schoenbach K. H.
Published: February 2005

A fluid model has been developed and used to help clarify the physical mechanisms occurring in microhollow cathode discharges (MHCD). Calculated current-voltage (I-V) characteristics and gas temperatures in xenon at 100 Torr are presented. Consistent with previous experimental results in similar conditions, we find a voltage maximum in the I-V characteristic. We show that this structure reflects a transition between a low-current, abnormal discharge localized inside the cylindrical hollow cathode to a higher-current, normal glow discharge sustained by electron emission from the outer surface of the cathode. This transition, due to the geometry of the device, is a factor contributing to the well-known stability of MHCDs.
Highly polarized absorption and photoluminescence of stretch-aligned single-wall carbon nanotubes dispersed in gelatin films
Authors: Kim Y. , Minami N. , Kazaoui S.
Published: February 2005

Substantial alignment of isolated individual single-wall carbon nanotubes (SWNTs) has been achieved by mechanically stretching gelatin films filled with homogeneously dispersed SWNTs. Highly polarized absorption and photoluminescence are observed that are attributed to interband optical transitions in SWNTs. Sharp and well-resolved spectral peaks comparable to those for an SWNT micelle suspension confirm good isolation of the tubes in dried films. Gelatin’s remarkable features such as miscibility with SWNT micelles, protective colloid, film-forming ability, and stretchability play important roles in the success. The realization of highly aligned and luminescent SWNT thin films should contribute to the development of SWNTs as novel optoelectronic materials.
Reversal behavior of exchange-biased submicron dots
Authors: Li Zhi-Pan , Petracic Oleg , Eisenmenger Johannes , Schuller Ivan K.
Published: February 2005

Nanostructured Fe dots were prepared on antiferromagnetic FeF2 thin films and investigated by magneto-optical Kerr effect (MOKE). We studied the influence of dot sizes on the magnetic hysteresis and compared the result with both continuous thin film bilayers and nanostructured Fe∕FeF2 pillars. Hysteresis loops were measured at temperatures below and above (10 and 90K, respectively) the Néel temperature of the antiferromagnet. A vortex state is found for dots of 300nm diameter, where the exchange bias field is reduced compared to larger dot system and the continuous bilayer. Micromagnetic simulations including the interaction with the antiferromagnet show qualitatively similar behavior.
Ferroelectric properties of wet-chemical patterned PbZr0.52Ti0.48O3 films
Authors: Ezhilvalavan S. , Samper Victor D.
Published: February 2005

Pb Zr 0.52 Ti 0.48 O 3 (PZT) films of thickness ∼1μm prepared by a sol-gel process were wet-chemically patterned using an economical and effective etch process. The etch recipe provided excellent etch control, minimized undercut, preserved the photoresist mask, and effectively removed the residues on the etched surfaces. A high etch rate (200nm∕min), high selectivity with respect to photoresist, and limited undercutting (1.5:1, lateral: thickness) were obtained. The patterned PZT films exhibited good ferroelectric properties in terms of larger saturation polarization, Pmax of ∼53μC∕cm2 at an applied field of 1MV∕cm, higher remnant polarization Pr of ∼30μC∕cm2 for a coercive field of ∼150kV∕cm, fatigue-free characteristics up to ⩾1010 switching cycles, and a low leakage current density of 10−6A∕cm2 at 200×105kV∕cm.
Thermal relaxation trimming for enhancement of extinction ratio in electro-optic polymer Mach-Zehnder modulators
Authors: Park Suntak , Ju Jung Jin , Park Seung Koo , Lee Myung-Hyun , Do Jung Yun
Published: February 2005

We propose and demonstrate a trimming method to enhance extinction ratio in an electro-optic (EO) polymer modulator with a Mach-Zehnder interferometer structure. In order to adjust the power splitting ratio at Y-branches, which is a main factor determining the extinction ratio, our method is exploited by using a change of the refractive index of the poled EO polymer due to thermal relaxation. The trimming is controlled by heating the Y-branch area via a heater. By using the thermal relaxation trimming, the extinction ratio in the adjusted EO modulator is enhanced by more than 7dB without excess loss.