bluuebunny/crossref_metadata_2025 huggingface dataset:
Early to middle Eocene history of the Arctic Ocean from Nd‐Sr isotopes in fossil fish debris, Lomonosov Ridge
Authors: Gleason J. D. , Thomas D. J. , Moore T. C. , Blum J. D. , Owen R. M. , Haley B. A.
Published: June 2009

Strontium and neodymium radiogenic isotope ratios in early to middle Eocene fossil fish debris (ichthyoliths) from Lomonosov Ridge (Integrated Ocean Drilling Program Expedition 302) help constrain water mass compositions in the Eocene Arctic Ocean between ∼55 and ∼45 Ma. The inferred paleodepositional setting was a shallow, offshore marine to marginal marine environment with limited connections to surrounding ocean basins. The new data demonstrate that sources of Nd and Sr in fish debris were distinct from each other, consistent with a salinity‐stratified water column above Lomonosov Ridge in the Eocene. The87Sr/86Sr values of ichthyoliths (0.7079–0.7087) are more radiogenic than Eocene seawater, requiring brackish to fresh water conditions in the environment where fish metabolized Sr. The87Sr/86Sr variations probably record changes in the overall balance of river Sr flux to the Eocene Arctic Ocean between ∼55 and ∼45 Ma and are used here to reconstruct surface water salinity values. The ɛNdvalues of ichthyoliths vary between −5.7 and −7.8, compatible with periodic (or intermittent) supply of Nd to Eocene Arctic intermediate water (AIW) from adjacent seas. Although the Norwegian‐Greenland Sea and North Atlantic Ocean were the most likely sources of Eocene AIW Nd, input from the Tethys Sea (via the Turgay Strait in early Eocene time) and the North Pacific Ocean (via a proto‐Bering Strait) also contributed.
Can flash heating of asperity contacts prevent melting?
Authors: Bizzarri A.
Published: June 2009

We solve the elasto‐dynamic problem for a 3‐D rupture, spontaneously propagating on a fault, obeying rate‐ and state‐dependent friction. We explore, through numerical simulations with physically realistic constitutive parameters, the effects on dynamic traction evolution of the flash heating of microscopic asperity contacts. Our results demonstrate that the inclusion of flash heating tends to increase the degree of instability of a homogeneous fault: the supershear rupture regime is favored, significantly larger stress drops are realized and weakening distance and fracture energy increase. We show that the key parameter which controls the temperature evolution and the activation of the flash heating is the slipping zone width, 2w. We found that for localized shear the rupture exhibits a pulse‐like behavior. On the contrary, for large slipping zones, the rupture develops as a sustained crack. Finally, we show that flash heating enhances the onset of melting.
“Medieval Warm Period” on the northern slope of central Tianshan Mountains, Xinjiang, NW China
Authors: Zhang Yun , Kong Zhao Chen , Yan Shun , Yang Zhen Jing , Ni Jian
Published: June 2009

“Medieval Warm Period” is used to describe a past climate epochs in Europe and neighboring regions from the ninth to the fourteenth centuries. In order to discuss the palaeoclimate changes during the MWP on the northern slope of central Tianshan Mountains in Xinjiang Autonomous Region, northwestern China, three Holocene sediment profiles in Daxigou region, Caotan Lake and Sichang Lake located in different elevations and vegetation zones were chosen for further discussion. A multi‐proxy reconstruction of the climate change in these three profiles using pollen, phytolith records, and the data of loss of ignition (LOI), grain size, and susceptibility showed that the climate was humid during the period corresponded in time with the MWP (from the middle of the Tang Dynasty to the middle of Yuan Dynasty). Complemented by tree‐ring record, other pollen records, data of plant seeds and historical documents; we conclude that during the MWP the climate was humid on the north slopes of Tianshan Mountains in Xinjiang.
Enhancement of phytoplankton primary productivity in the southern East China Sea following episodic typhoon passage
Authors: Siswanto Eko , Morimoto Akihiko , Kojima Shoichiro
Published: June 2009

The enhancement of primary productivity (PPenh) in the southern East China Sea (ECS) following 16 typhoon passages was investigated using ocean color data and a primary productivity model. PPenh tended to be higher when typhoons traversed slowly with trajectories that allowed strong southerly winds to prevail over Yonaguni Island. Such long‐lasting southerly winds were believed to push the Kuroshio current axis shelfward, enhancing the upwelling of nutrients, hence promoting new productivity (NP). The importance of long‐lasting southerly winds as a proxy for physical perturbations underlying PPenh was expressed by an empirical equation by which 88% of PPenh variation could be explained. Applying this equation, we assessed that typhoon passages accounted for a minimum of 0.6–11.8% of the ECS summer–fall NP, suggesting that typhoon passage over the southern ECS is an important phenomenon supporting NP in the ECS.
First simultaneous observations of daytime MSTIDs over North America using GPS‐TEC and DEMETER satellite data
Authors: Onishi Tatsuo , Tsugawa Takuya , Otsuka Yuichi , Berthelier Jean‐Jacques , Lebreton Jean‐Pierre
Published: June 2009

We present simultaneous observations of daytime medium‐scale traveling ionospheric disturbances (MSTIDs) over North America, using measurements of the Total Electron Content (TEC) by the US GPS network and ionospheric plasma data from the DEMETER micro‐satellite. Several events show latitudinal variations of the plasma parameters at satellite altitude corresponding to the MSTID structures revealed on 2D TEC maps. In a case study with a very well defined MSTID, quasi periodic variations of the plasma density and of the ion velocity parallel to the Earth's magnetic field are observed along the satellite orbit that match the signature of the MSTID on the TEC maps. We believe it is the first simultaneous observation of parallel plasma motion in the topside ionosphere and propagating MSTID structures in the F‐region. An initial analysis of this event is performed in the light of results from simple model of ionospheric disturbances associated with Atmospheric Gravity Waves (AGWs).
Pre‐monsoon zonal wind Index over Tibetan Plateau and sub‐seasonal Indian summer monsoon rainfall variability
Authors: Dugam S. S. , Bansod S. D. , Kakade S. B.
Published: June 2009

In this paper, by using the Principal Component Analysis (PCA) technique monthly zonal wind indices over Tibetan Plateau (25°N–45°N, 75–105°E) (TP) at 200 hPa have been constructed for the period 1948–2006. These indices are referred as Tibetan Zonal Wind Index (TZWI). The relationship between the TZWI and Indian summer monsoon rainfall on monthly basis has been studied by the correlation analysis. From the analysis, it is observed that pre‐monsoon months (April and May) of TZWI show the significant inverse relationship with June and July rainfall over India respectively. The study may be useful for forecasting rainfall activity in June and July months, which are crucial months from the agricultural point of view.
A Phase-Contrast MRI Study of Physiologic Cerebral Venous Flow
Authors: Stoquart-ElSankari Souraya , Lehmann Pierre , Villette Agnès , Czosnyka Marek , Meyer Marc-Etienne , Deramond Hervé , Balédent Olivier
Published: June 2009

Although crucial in regulating intracranial hydrodynamics, the cerebral venous system has been rarely studied because of its structural complexity and individual variations. The purpose of our study was to evaluate the organization of cerebral venous system in healthy adults. Phase-contrast magnetic resonance imaging (PC-MRI) was performed in 18 healthy volunteers, in the supine position. Venous, arterial, and cerebrospinal fluid (CSF) flows were calculated. We found heterogeneous individual venous flows and variable side dominance in paired veins and sinuses. In some participants, the accessory epidural drainage preponderated over the habitually dominant jugular outflow. The PC-MRI enabled measurements of venous flows in superior sagittal (SSS), SRS (straight), and TS (transverse) sinuses with excellent detection rates. Pulsatility index for both intracranial (SSS) and cervical (mainly jugular) levels showed a significant increase in pulsatile blood flow in jugular veins as compared with that in SSS. Mean cervical and cerebral arterial blood flows were 714 ± 124 and 649 ± 178 mL/min, respectively. Cerebrospinal fluid aqueductal and cervical stroke volumes were 41 ± 22 and 460 ± 149 μL, respectively. Our results emphasize the variability of venous drainage for side dominance and jugular/epidural organization. The pulsatility of venous outflow and the role it plays in the regulation of intracranial pressure require further investigation.
Decrease of Nicotinic Receptors in the Nigrostriatal System in Parkinson's Disease
Authors: Kas Aurélie , Bottlaender Michel , Gallezot Jean Dominique , Vidailhet Marie , Villafane Gabriel , Grégoire Marie Claude , Coulon Christine , Valette Héric , Dollé Frédéric , Ribeiro Maria-Joao , Hantraye Philippe , Remy Philippe
Published: June 2009

Smoking is associated with a lower incidence of Parkinson's disease (PD), which might be related to a neuroprotective action of nicotine. Postmortem studies have shown a decrease of cerebral nicotinic acetylcholine receptors (nAChRs) in PD. In this study, we evaluated the decrease of nAChRs in PD in vivo using positron emission tomography (PET), and we explored the relationship between nAChRs density and PD severity using both clinical scores and the measurement of striatal dopaminergic function. Thirteen nondemented patients with PD underwent two PET scans, one with 6-[18F]fluoro-3,4-dihydroxy-l-phenylalanine (6-[18F]fluoro-l-DOPA) to measure the dopaminergic function and another with 2-[18F]fluoro-3-[2( S)-2-azetidinylmethoxy]pyridine (2-[18F]fluoro-A-85380), a radiotracer with high affinity for the nAChRs. Distribution volumes (DVs) of 2-[18F]fluoro-A-85380 measured in the PD group were compared with those obtained from six nonsmoking healthy controls, with regions-of-interest and voxel-based approaches. Both analyses showed a significant ( P<0.05) decrease of 2-[18F]fluoro-A-85380 DV in the striatum (10%) and substantia nigra (14.9%) in PD patients. Despite the wide range of PD stages, no correlation was found between DV and the clinical and PET markers of PD severity.
Consistency of Hearing Aid Use in Infants With Early-Identified Hearing Loss
Authors: Moeller Mary Pat , Hoover Brenda , Peterson Barbara , Stelmachowicz Pat
Published: June 2009

Purpose

To examine the consistency of hearing aid use by infants. A goal was to identify maternal, child, and situational factors that affected consistency of device use.

Method

Maternal interviews were conducted using a nonvalidated structured interview (Amplification in Daily Life Questionnaire
)
that included 5-point Likert scale items and open-ended questions. Participants were mothers of 7 infants with mild to moderately severe hearing loss who were enrolled in a longitudinal study. Data were collected at 4 intervals (10.5–12, 16.5, 22.5, and 28.5 months old).

Results

Consistency of amplification use was variable at early ages but improved with age. By age 28.5 months, toddlers used amplification regularly in most settings. Selected daily situations (e.g., in car or outdoors) were more challenging for maintaining device use than contexts where the child was closely monitored. Only 2 families established early, consistent full-time use across all contexts examined. Qualitative results were used to identify familial, developmental, and situational variables that influenced the consistency of infant/toddler device use.

Conclusion

Families may benefit from audiologic counseling that acknowledges the multifaceted challenges that arise. Audiologists can work in partnership with families to promote consistent device use across a variety of daily situations.
Do Experienced Hearing Aid Users Know How to Use Their Hearing Aids Correctly?
Authors: Desjardins Jamie L. , Doherty Karen A.
Published: June 2009

Purpose

To assess experienced hearing aid users' ability to use their hearing aids correctly.

Method

In this study, we developed the Practical Hearing Aid Skills Test (PHAST) to objectively test a hearing aid user’s ability to manipulate his or her hearing aids. The PHAST requires hearing aid users to perform 8 hearing aid care and use tasks that are basic skills typically taught to new hearing aid users at the time of their hearing aid fitting. The PHAST was administered to a group of 50 experienced hearing aid users. In addition, participants were administered questionnaires about hearing aid satisfaction (i.e., Satisfaction With Amplification in Daily Life; R. M. Cox & G. C. Alexander, 1999), benefit (i.e., Abbreviated Profile of Hearing Aid Benefit; R. M. Cox & G. C. Alexander, 1995), and use.

Results

Participants' performance on the PHAST ranged from 48% to 100%, and the scores were normally distributed around the mean (78.56%). No significant relationship was observed between the PHAST and any of the other tests administered in this study. The only variable significantly associated with participants' performance on the PHAST was age.

Conclusions

Results from this study suggest that experienced hearing aid users range from having an excellent understanding of how to use their hearing aids to a poor understanding. The variability in performance among experienced hearing aid users highlights the importance of directly assessing a client’s ability to use his or her hearing aids.
Pinpoint: A Design Study in Interactive Visualization for Finding People in a Large Organization
Authors: Forsén Gunnar , Lundin Thomas , Löwgren Jonas
Published: June 2009

This design study reports on how information visualization was applied to the common problem for knowledge workers to find people with relevant expertise and interests in a large organization. The outcome is the Pinpoint concept, an interactive visualization where the user's most closely related colleagues are presented radially for browsing, filtering and further exploration of the topical networks of the organization. Based on design reasoning and empirical validation, we claim that the concept approaches desirability as well as usefulness and usability in its intended use situation. We further argue that it is feasible for deployment under certain conditions, and that it is applicable in a range of large organizations if organization-specific policies and standards are taken into account.
The bipolar doping of ZnS via native defects and external dopants
Authors: Gai Yanqin , Li Jingbo , Yao Bin , Xia Jian-Bai
Published: June 2009

By employing first-principle total-energy calculations, a systematic study of the dopability of ZnS to be both n- and p-types compared with that of ZnO is carried out. We find that all the attempted acceptor dopants, group V substituting on the S lattice site and group I and IB on the Zn sites in ZnS, have lower ionization energies than the corresponding ones in ZnO. This can be accounted for by the fact that ZnS has relative higher valence band maximum than ZnO. Native ZnS is weak p-type under S-rich condition, as the abundant acceptor VZn has rather large ionization energy. Self-compensations by the formation of interstitial donors in group I and IB-doped p-type ZnS can be avoided when sample is prepared under S-rich condition. In terms of ionization energies, LiZn and NS are the preferred acceptors in ZnS. Native n-type doping of ZnS is limited by the spontaneous formation of intrinsic VZn2−; high efficient n-type doping with dopants is harder to achieve than in ZnO because of the readiness of forming native compensating centers and higher ionization energy of donors in ZnS.
Photoelectron emission from solid Ne tested by impurity adsorption
Authors: Dmitriev Yu. A.
Published: June 2009

Electron emission is obtained from a solid Ne sample growing from the gas phase on a low temperature substrate. The surface of the sample is irradiated by the light of an open-source microwave discharge running in the gaseous Ne. A second gas flow of CH4 is simultaneously passed onto the substrate, avoiding the discharge zone. Free electrons ejected into a vacuum chamber during the sample growth are detected by means of the electron cyclotron resonance (ECR) technique. The electron yield is found to decrease with increasing CH4 flow. Fitting curves to the experimental data show that the surface CH4 impurities play the major role in emission quenching. A temperature effect was observed in which a 4.2K sample was much more sensitive to CH4 doping than a 1.6K one. Based on the experimental results, a model is proposed for the surface sites where electrons escape the solid.
On kinetic features of photo- or γ-induced polymerization in p-diethynylbenzene crystals in the temperature range 4.2–300K
Authors: Gordon D. A. , Mikhaylov A. I.
Published: June 2009

The stereoregular radical polymerization in photo- or γ-irradiated crystals of p-diethynylbenzene (DEB) has been found to proceed in the temperature range of 4.2–300K [J. Low Temp. Phys. 139, 675 (2005)]. We investigate the kinetics of this process. The polymerization of acetylene monomers due to the system of conjugated bonds formation results in the shift of a crystal absorption band from UV to visible. When compared with gravimetrical data on the polymer yield, it allows the direct detection of polymerization process in a crystal. The monomer radicals initiating the polymerization process, as well as propagating macroradicals, are detected by the ESR method. The rates of both radical formation and chemical reaction of polymerization are retarded, as is inherent to solid-phase processes, already at low yields. Thus we are applying a mechanism that pertains to the first stages of the processes only. It is proved that both photo- and γ-induced polymerization have chain character in the temperature range 77–300K but it is most probably not chained at 4.2K and, for photo-polymerization, every act of monomer addition to the polymer needs an extra quantum of light. The kinetic chain length (the number of added monomer molecules per radical) turn out to be around of 200 at 300K and of 20 at 77K. It is interesting to note that polymer just formed is able to be modified—the radicals newly created in a polymer chain are able to add monomer molecules, forming, in such a way, a branched polymer. This process, of course, is unchained, too.
Thermal diffusivity of aromatic polyimide thin films by temperature wave analysis
Authors: Morikawa Junko , Hashimoto Toshimasa
Published: June 2009

The heat transport properties of aromatic polyimide thin films have become more important in the use for the electric insulation in the microelectronic devices with highly integrated circuits. The various kinds of measuring methods have been applied to obtain the anisotropic thermal conductivity and thermal diffusivity of thin films, however, if the specimens are soft and transparent, the conventional methodology requires highly advanced technology in preparing the specimens for the measurement and the results obtained vary widely. The purpose of this study is to apply the temperature wave analysis (TWA) method to measure the thermal diffusivity of thin films and spin-coated layers of aromatic polyimide in the thickness direction at various temperatures. The TWA is an absolute method to determine the thermal diffusivity by using the phase shift of temperature wave. We have performed measurements on the five different chemical structures of aromatic polyimide, including polyimide isoindoloquinazolinedione (PIQ), pyromellitic dianhydride and 4,4′-oxydianiline (PMDA/ODA), 3,3′,4,4′,-biphenyltetracarboxylic dianhydride and p-phenylenediamine (BPDA/PPDA), 3,3′,4,4′-biphenyltetracarboxylic dianhydride and 4,4′-oxydianiline (BPDA/ODA), and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride and 3,3′-diaminobenzophenone (BTDA/DAB). As a result, thermal diffusivity of thin films in a thickness range from 0.1 to 300 μm at a temperature range from 10 to 570 K is obtained. The thickness dependence of thermal diffusivity of spin-coated layers of PIQ exhibits a good coincidence with the tendency of molecular anisotropy observed by attenuated total reflection Fourier transform infrared spectroscopy. In the low temperature below 20 K the amorphous PMDA/ODA film exhibits a substantial increase, which can be understood by considering the phonon mean free path of amorphous systems as first noted by Kittel for inorganic glasses. The glass transition of BTDA/DAB is observed as a rapid decrease of thermal diffusivity. The results indicate the availability of TWA for the present needs of accurate but simple measuring technique to determine the thermal diffusivity of thin polymer films, which is strongly dependent on the chemical and anisotropic structures.
Nonadiabatic small polarons, positive magnetoresistance, and ferrimagnetism behavior in the partially inverse Mn2−xV1+xO4 spinels
Authors: Pannunzio-Miner E. V. , De Paoli J. M. , Carbonio R. E. , Sánchez R. D.
Published: June 2009

We present experimental results of electrical resistivity (ρ), magnetoresistance (MR), Seebeck coefficient (S), and magnetic susceptibility (χ) experiments at high temperature on the spinel Mn2−xV1+xO4 series with x=0, 13, and 1, prepared by solid state reaction. The Rietveld analysis of neutron powder diffraction (NPD) patterns confirm the expected cubic symmetry (SG: Fd-3m) with cell parameters around 8.5 Å. We also precisely calculate the distribution of Mn/V cations, in the tetrahedral and octahedral sites, for the whole series showing an important degree of inversion. The magnetic susceptibility and electrical transport properties show ferrimagnetic and semiconductor behaviors, respectively. A large difference detected between the activation energies for S and ρ indicates the presence of small polarons and the temperature dependence of ρ is well fitted with the nonadiabatic polarons model. All the samples present positive MR at room temperature, in particular, the highest value (around 1%) was observed in the MnV2O4 sample.
Modeling the cell-type dependence of diffusion-limited intracellular ice nucleation and growth during both vitrification and slow freezing
Authors: Yang Geer , Zhang Aili , Xu Lisa X. , He Xiaoming
Published: June 2009

In this study, a set of models for predicting the diffusion-limited ice nucleation and growth inside biological cells were established. Both the heterogeneous and homogeneous nucleation mechanisms were considered in the models. Molecular mobility including viscosity and mutual diffusion coefficient of aqueous cryoprotectant (i.e., glycerol here) solutions was estimated using models derived from the free volume theory for glass transition, which makes it possible to predict the two most important physical properties (i.e., viscosity and mutual diffusion coefficient) over wide ranges of temperature and concentration as encountered in cryopreservation. After being verified using experimental data, the models were used to predict the critical cooling rate (defined as the cooling rate required so that the crystallized volume is less than 0.1% of the cell volume) as a function of the initial glycerol concentration in a number of cell types with different sizes. For slowing freezing, it was found that the required critical cooling rate is cell-type dependent with influences from cell size and the ice nucleation and water transport parameters. In general, the critical cooling rate does not change significantly with the initial glycerol concentration used and tends to be higher for smaller cells. For vitrification, the required critical cooling rate does change significantly with the initial glycerol concentration used and tends to decrease with the decrease in cell size. However, the required critical cooling rate can be similar for cells with very different sizes. It was further found that the thermodynamic and kinetic parameters for intracellular ice formation associated with different cells rather than the cell size per se significantly affect the critical cooling rates required for vitrification. For all cell types, it was found that homogeneous nucleation dominates at ultrafast cooling rates and/or high glycerol concentrations, whereas heterogeneous nucleation becomes important only during slow freezing with a low initial glycerol concentration (<1.5–2M), particularly for large cells such as mouse oocytes.
Magnetotransport in polycrystalline La2/3Sr1/3MnO3 thin films of controlled granularity
Authors: Muduli P. K. , Singh Gyanendra , Sharma R. , Budhani R. C.
Published: June 2009

Polycrystalline La2/3Sr1/3MnO3 thin films were synthesized by pulsed laser ablation on single crystal (100) yttria-stabilized zirconia substrates to investigate the mechanism of magnetotransport in a granular manganite. Different degrees of granularity are achieved by using the deposition temperatures (TD) of 700 and 800 °C. Although no significant change in magnetic order temperature (TC) and saturation magnetization is seen for these two types of films, the temperature and magnetic field dependence of their resistivity (ρ(T,H)) is strikingly dissimilar. While the ρ(T,H) of the 800 °C film is comparable to that of epitaxial samples, the lower growth temperature leads to a material which undergoes insulator-to-metal transition at a temperature (TP≈170 K) much lower than TC. At T⪡TP, the resistivity is characterized by a minimum followed by ln T divergence at still lower temperatures. The high negative magnetoresistance (≈20%) and ln T dependence below the minimum are explained on the basis of Kondo-type scattering from blocked Mn spins in the intergranular material. Further, a striking feature of the TD=700 °C film is its two orders of magnitude larger anisotropic magnetoresistance (AMR) as compared to the AMR of epitaxial films. We attribute it to unquenching of the orbital angular momentum of 3d electrons of Mn ions in the intergranular region where crystal field is poorly defined.
Ultrawideband dielectric spectroscopy of BaZrxTi1−xO3 ceramics and its microscopic mechanism of polarization
Authors: Teranishi Takashi , Hoshina Takuya , Takeda Hiroaki , Tsurumi Takaaki
Published: June 2009

Ultrawideband dielectric spectroscopy analysis of barium zirconate titanate (BaZrxTi1−xO3, BZT) ceramics at different temperatures disclosed the contribution of both the dipole and the ionic polarizations to permittivity at around dielectric maximum temperature (Tm). In BaZr0.25Ti0.75O3 ceramics, the permittivity around Tm is dominated by the temperature dependence of the permittivity determined by the dipole polarization (εdipole). In relaxor ferroelectrics, the diffuse dielectric response around Tm could be derived from the temperature dependence of εdipole. The variation of εdipole with temperature could be also explained by the growth process of polar nanoregions (PNRs) and the damping process of the thermal fluctuation of dipoles in PNRs.
Out-of-plane thermal diffusivity measurement of transparent thin film by the acoustic grating excitation
Authors: Ivakin E. V. , Karelin M. U. , Sukhadolau A. V.
Published: June 2009

The theory of pulsed photoacoustic phase method for out-of-plane thermal diffusivity measurement of thin dielectric film deposited on highly absorbing substrate is developed. The method is based on spatial modulation of the intensity of excitation. Optical detection of acoustic waves enables working with acoustic frequencies higher than 107 Hz and allows characterization of transparent films of submicron thickness. Pilot measurements have been carried out with SiO2 films on monocrystalline silicon wafer. Thermal diffusivity determined in the experiment agrees with the reference value for the bulk fused quartz.
Resistive state due to an ac electromagnetic field in a wide superconducting film
Authors: Dmitriev V. M. , Zolochevskiĭ I. V.
Published: June 2009

It is shown experimentally that, by analogy with a narrow channel and high-frequency phase-slip centers (ac PSC), high-frequency phase-slip lines (ac PSL) arise in a wide superconducting film irradiated with an external microwave field whose power exceeds a critical value Pc. For a dc probe current much weaker than the critical current, such a state is found to be resistive; this manifests as linear initial sections of the current-voltage characteristics (IVCs), reflecting the voltage drop on ac PSL. It is shown that for monotonically varying power of the electromagnetic irradiation field the slope of the linear sections of the IVCs changes discretely and is a multiple of the resistance of an ac PSL which arises at power Pc.
Linear diatomic crystal: single-electron states and large-radius excitons
Authors: Adamyan V. M. , Smyrnov O. A.
Published: June 2009

The large-radius exciton spectrum in a linear crystal with two atoms in the unit cell is obtained using the single-electron eigenfunctions and band structure found by the zero-range potentials method. The ground-state exciton binding energies for the linear crystal in vacuum turn out to be larger than the corresponding energy gaps for any set of the crystal parameters.
The relation between fractional statistics and finite bosonic systems in the one-dimensional case
Authors: Rovenchak A.
Published: June 2009

The equivalence is established between a one-dimensional (1D) Bose system with a finite number of particles and a system obeying fractional (intermediate) Gentile statistics, in which the maximum occupation of single-particle energy levels is limited. A system of 1D harmonic oscillators, providing a model for a harmonically trapped Bose gas, is considered. The results are generalized for a system with a power-law energy spectrum.
Sizing and burn time measurements of micron-sized metal powders
Authors: Gill Robert J. , Mohan Salil , Dreizin Edward L.
Published: June 2009

Detailed ignition and combustion mechanisms are needed to develop optimized propellant and energetic formulations using micron-sized metal powders, such as aluminum. Combustion researchers have traditionally used relatively coarse metal particles to characterize the burn time dependence on particle size. However, measurements of burn times for particles below 10 μm in diameter are still needed for aluminum powders and other metal fuels. The apparatus described here sizes the particles just before the ignition event, providing a direct correlation between individual particle size and its burn time. Two lasers were utilized: a 785 nm laser diode for sizing the particles and a 125 W CO2 laser for particle ignition. The particles crossed the 785 nm laser beam just before crossing the CO2 laser beam. The particle size was determined from the amplitude of the scattered 785 nm light pulse. The burn time was determined from the duration of the visible light emission produced from the ignited particle. The in situ measured particle size distributions compared well with the size distributions measured for the same powders by a commercial instrument using low angle laser light scattering. Our measurements with two nominally spherical aluminum powders, suggest that the burn times increase from 0.5 to ∼2.5 ms as the particle diameters increase from 3 to 8 μm.
Study of interfacial defects induced during the oxidation of ultrathin strained silicon layers
Authors: Ioannou-Sougleridis V. , Kelaidis N. , Tsamis C. , Skarlatos D. , Krontiras C. A. , Georga S. N. , Komninou Ph. , Kellerman B. , Seacrist M.
Published: June 2009

In this work ultrathin strained silicon layers grown on relaxed Si0.9Ge0.1 substrates were oxidized under high thermal budget conditions in N2O ambient at 800 °C. The results indicate that the density of interface traps depends on the extent of the oxidation process. If the strained Si layer is totally consumed the density of interface traps reduces to almost half the value as compared to the case where a part of the strained Si layer still remains. The results indicate that the two existing interfaces of the strained Si layer, the SiO2/strained-Si and the strained-Si/Si0.9Ge0.1, contribute in parallel to the measured interface trap density. In addition, the buried strained-Si/Si0.9Ge0.1 interface constitutes a major source of the observed high density of interface traps.
Luminescence enhancement and emission color adjustment of white organic light-emitting diodes with quantum-well-like structures
Authors: Yang Su-Hua , Hong Bo-Cheng , Huang Shih-Fong
Published: June 2009

In recent years, white-light organic light-emitting diodes (OLEDs) have attracted considerable attention because of their potential applications in displays, backlight units, and general lighting. In this paper, we describe the fabrication of a high-luminance white-light OLED with dual-emission layers (EMLs). The 2,9-dimethyl-4,7-diphenyl-1,10-phenanhroline hole blocking layers (HBLs) were prepared to enhance the luminance and adjust the emission color of the device. For the device with a single-HBL structure, the excess holes were accumulated at the red EML (REML)/HBL1 interface. Consequently, most of the carriers were recombined in the REML, which led to a redshifted light emission. On the contrary, the device with a dual-HBL structure showed a blueshifted light emission. The device with a quantum-well-like structure increased the carrier trapping and recombination probabilities; as a result, a lower current density and a higher luminance intensity of the device were achieved. The maximum luminance intensity was 33 600 cd/m2 at 13 V, with CIE coordinates at (0.32, 0.32); the maximum current efficiency was 7.06 cd/A at 10 V; and the maximum power efficiency was 2.62 lm/W at 7 V and 294 cd/m2.
Optical properties of aluminum-, gallium-, and indium-doped Bi4Ti3O12 thin films
Authors: Jia Caihong , Chen Yonghai , Zhang W. F.
Published: June 2009

Undoped and Al-, Ga-, and In-doped Bi4Ti3O12 thin films were prepared on fused quartz substrates by chemical solution deposition. Their microstructures and optical properties were investigated by x-ray diffraction and UV-visible-NIR spectrophotometer, respectively. The optical band-gap energies, Urbach energies, and linear refractive indices of all the films are derived from the transmittance spectrum. Following the single oscillator model, the dispersion parameters such as the average oscillator energy (E0) and dispersion energy (Ed) are achieved. The energy band gap and refractive indices are found to decrease with introducing the dopants of Al, Ga, and In, which is useful for the band-gap engineering and optical waveguide devices. The refractive index dispersion parameter (E0/S0) increases and the chemical bonding quantity (β) decreases in all the films compared with those of bulk. It is supposed to be caused by the nanosize grains in films.
Transport scaling in interchange-driven toroidal plasmas
Authors: Ricci Paolo , Rogers B. N.
Published: June 2009

Two-dimensional fluid simulations of a simple magnetized torus are presented, in which the vertical and toroidal components of the magnetic field create helicoidal field lines that terminate on the upper and lower walls of the plasma chamber. The simulations self-consistently evolve the full radial profiles of the electric potential, density, and electron temperature in the presence of three competing effects: the cross-field turbulent transport driven by the interchange instability, parallel losses to the upper and lower walls, and the input of particles and heat by external plasma sources. Considering parameter regimes in which equilibrium E×B shear flow effects are weak, we study the dependence of the plasma profiles—in particular the pressure profile scale length—on the parameters of the system. Analytical scalings are obtained that show remarkable agreement with the simulations.
Blueshift of optical band gap in c-axis oriented and conducting Al-doped ZnO thin films
Authors: Di Trolio A. , Bauer E. M. , Scavia G. , Veroli C.
Published: June 2009

We have investigated the structural, optical, and electrical properties of alumina-doped zinc oxide (AZO) thin films, grown by pulsed laser deposition. The optical transmittance of the films is over 80% in the visible region, and the absorption edge shifts from about 380 nm of the undoped sample to 320 nm of the AZO film. The calculated optical band gap (Eg) of 2 wt % AZO films shows a widening up to 3.82 eV with respect to the undoped film (3.28 eV). Higher doping concentration (6 wt %) leads to films with larger Eg (4.1 eV), but also epitaxial properties are affected. A further widening of the gap occurs when the AZO films are deposited by lowering the substrate temperature (Ts) from 450 to 250 °C. These blueshifts are respectively attributed to the increase in carrier concentration, induced by Al-donor doping, and also a lower degree of crystalline order. AZO films with doping concentration of 2 wt % show resistivity values of about 10−3 Ω cm and the local I-V curves, measured by scanning tunneling spectroscopy, show higher tunneling current than ZnO film. The Al-doping route proved to be effective in tailoring the optical and electrical properties without essentially affecting the crystalline structure of the films.
Electronic and optical properties of electrochemically polymerized polycarbazole/aluminum Schottky diodes
Authors: Singh Arun Kumar , Dwivedi A. D. D. , Chakrabarti P. , Prakash Rajiv
Published: June 2009

We report the fabrication of organic Schottky diodes on indium tin oxide (ITO) coated glass by electrochemically polymerized polycarbazole (PCz) with configuration ITO/PCz/Al. The diode has been characterized in respect of electrical and optical properties. The study involves estimation of optical bandgap of the polymer from UV-visible spectroscopic measurements. The current-voltage (J-V) and capacitance-voltage (C-V) characteristics of the Schottky diode were subsequently used for extracting electronic parameters of the device such as ideality factor, barrier height, reverse saturation current, built-in potential, depletion width, doping concentration, etc. The photoresponse of the Schottky contact was measured by illuminating the device with a laser source operating at 650 nm having an incident optical power density of 10 mW/cm2. The device exhibits a high value of peak detectivity (∼107 cm Hz1/2 W−1) near zero bias voltage and the same attains a value of the order of 109 cm Hz1/2 W−1 at a reverse bias of −6 V.
Quantum effects on the Rayleigh–Taylor instability in a horizontal inhomogeneous rotating plasma
Authors: Hoshoudy G. A.
Published: June 2009

The Rayleigh–Taylor instability is studied analytically in inhomogeneous plasma rotating uniformly in an external transverse magnetic field. The influence of the quantum mechanism is considered. For a stratified layer the linear growth rate is obtained. Some special cases that isolate the effect of various parameters on the growth rate of the Rayleigh–Taylor instability are discussed. It is shown that for some cases, the presence of the external transverse magnetic field beside the quantum effect will bring about more stability on the Rayleigh–Taylor instability.
Development of a dual-modal tissue diagnostic system combining time-resolved fluorescence spectroscopy and ultrasonic backscatter microscopy
Authors: Sun Yang , Park Jesung , Stephens Douglas N. , Jo Javier A. , Sun Lei , Cannata Jonathan M. , Saroufeem Ramez M. G. , Shung K. Kirk , Marcu Laura
Published: June 2009

We report a tissue diagnostic system which combines two complementary techniques of time-resolved laser-induced fluorescence spectroscopy (TR-LIFS) and ultrasonic backscatter microscopy (UBM). TR-LIFS evaluates the biochemical composition of tissue, while UBM provides tissue microanatomy and enables localization of the region of diagnostic interest. The TR-LIFS component consists of an optical fiber-based time-domain apparatus including a spectrometer, gated multichannel plate photomultiplier, and fast digitizer. It records the fluorescence with high sensitivity (nM concentration range) and time resolution as low as 300 ps. The UBM system consists of a transducer, pulser, receiving circuit, and positioning stage. The transducer used here is 45 MHz, unfocused, with axial and lateral resolutions 38 and 200 μm. Validation of the hybrid system and ultrasonic and spectroscopic data coregistration were conducted both in vitro (tissue phantom) and ex vivo (atherosclerotic tissue specimens of human aorta). Standard histopathological analysis of tissue samples was used to validate the UBM-TRLIFS data. Current results have demonstrated that spatially correlated UBM and TR-LIFS data provide complementary characterization of both morphology (necrotic core and calcium deposits) and biochemistry (collagen, elastin, and lipid features) of the atherosclerotic plaques at the same location. Thus, a combination of fluorescence spectroscopy with ultrasound imaging would allow for better identification of features associated with tissue pathologies. Current design and performance of the hybrid system suggests potential applications in clinical diagnosis of atherosclerotic plaque.
Canonical quantization of electromagnetic field in an anisotropic polarizable and magnetizable medium
Authors: Amooshahi M.
Published: June 2009

A fully canonical quantization of electromagnetic field is introduced in the presence of an anisotropic polarizable and magnetizable medium. Two tensor fields which couple the electromagnetic field with the medium and have an important role in this quantization method are introduced. The electric and magnetic polarization fields of the medium naturally are concluded in terms of the coupling tensors and the dynamical variables modeling the magnetodielectric medium. In Heisenberg picture, the constitutive equations of the medium together with the Maxwell laws are obtained as the equations of motion of the total system and the susceptibility tensors of the medium are calculated in terms of the coupling tensors. Following a perturbation method the Green function related to the total system is found and the time dependence of electromagnetic field operators is derived.
Experimental device to measure the electrical and optical properties of radiochromic films as a function of temperature
Authors: Gómez-Galván F. , Mercado-Uribe H.
Published: June 2009

In the last decade, radiochromic films (RCF) have been used extensively in medical physics for evaluating uniformity of radiation beams and dose distributions. These films are very sensitive to changes in temperature; therefore, one needs to know its thermal behavior to use them efficiently. Normally, the thermal assessment is done using optical methods on previously irradiated samples. Here, we report the use of a complementary dielectric method. We designed an experimental device that allows us to measure, simultaneously, the dielectric and optical properties as a function of temperature. We performed the measurements in real-time to temperature increases from 27 to 48 °C of EBT and MD-55 RCF previously exposed to UV. We found for both films a decrease in the real part of the dielectric permittivity as the temperature increases, but an increment and decrease in the dielectric loss factor for the EBT and MD-55 film, respectively.
Linear and nonlinear optical characterizations of a monomeric symmetric squaraine-based dye in solution
Authors: Toro Carlo , De Boni Leonardo , Yao Sheng , Ritchie James P. , Masunov Artëm E. , Belfield Kevin D. , Hernandez Florencio E.
Published: June 2009

The photophysical properties of a symmetric squaryllium dye, namely, 2,4-bis[4-(N,N-dibutylamino)-2-hydroxyphenyl] squaraine (SQ), in its monomer form in acetone solution, have been thoroughly studied by means of one-photon absorption (1PA) and two-photon absorption (2PA), excitation anisotropy, fluorescence emission, fluorescence quantum yield, and excited state absorption. The results show that there is a strong one-photon allowed absorption band in the near IR region associated with intramolecular charge transfer. Higher one-photon allowed and forbidden singlet excited states were also revealed by absorption and excitation anisotropy. A relatively high fluorescence quantum yield (0.44) was measured for this dye. The nonlinear optical characterization of SQ in solution confirms the ability of squaraine dyes to be used as good two-photon absorbers. Additionally, it was found that this dye presents both saturable and reverse saturable absorption effects. Density functional theory calculations of the 1PA and 2PA electronic spectra of SQ were carried out to support the experimental data. A detailed analysis of the symmetry and energy of the orbitals involved in the lowest five electronic transitions is presented and discussed in relation to the behavior observed experimentally.
The optimal Seebeck coefficient for obtaining the maximum power factor in thermoelectrics
Authors: Pichanusakorn P. , Bandaru P. R.
Published: June 2009

We propose the existence of an optimal Seebeck coefficient (Sopt) for three-, two-, and one-dimensional thermoelectric materials. This assertion is supported by an exhaustive comparison with experimental data of well characterized bulk thermoelectrics, all of which have shown that the power factor is maximized when Sopt in the range of 130–187 μV/K. Our study serves as a quick guideline for the optimization of thermoelectric materials, and makes the point that efforts should be focused on increasing the electrical conductivity (σ) at the given Sopt.
Electrical detection of spin precession in single layer graphene spin valves with transparent contacts
Authors: Han Wei , Pi K. , Bao W. , McCreary K. M. , Li Yan , Wang W. H. , Lau C. N. , Kawakami R. K.
Published: June 2009

Spin accumulation and spin precession in single layer graphene are studied by nonlocal spin valve measurements at room temperature. The dependence of the nonlocal magnetoresistance on electrode spacing is investigated and the results indicate a spin diffusion length of ∼1.6 μm and a spin injection/detection efficiency of 0.013. Electrical detection of the spin precession confirms that the nonlocal signal originates from spin injection and transport. Fitting of the Hanle spin precession data yields a spin relaxation time of ∼84 ps and a spin diffusion length of ∼1.5 μm, which is consistent with the value obtained through the spacing dependence.
Hydrogen sorption in Pd-decorated Mg–MgO core-shell nanoparticles
Authors: Callini E. , Pasquini L. , Piscopiello E. , Montone A. , Antisari M. Vittori , Bonetti E.
Published: June 2009

Mg nanoparticles with metal-oxide core-shell morphology were synthesized by inert-gas condensation and decorated by in situ Pd deposition. Transmission electron microscopy and x-ray diffraction underline the formation of a noncontinuous layer with Pd clusters on top of the MgO shell. Even in the presence of a thick MgO interlayer, a modest (2 at. %) Pd decoration deeply enhances the hydrogen sorption properties: previously inert nanoparticles exhibit metal-hydride transformation with fast kinetics and gravimetric capacity above 5 wt %.
Lagrangian particles with mixing. II. Sparse-Lagrangian methods in application for turbulent reacting flows
Authors: Klimenko A. Y.
Published: June 2009

Both parts of this work present a more detailed and specific analysis of ideas introduced in the previously published letter [Phys. Fluids 19, 031702 (2007)]. In Paper I [Phys. Fluids 19, 065101 (2009)], we show that the continuous scalar transport and diffusion can be accurately specified by means of mixing between randomly walking Lagrangian particles with scalar properties. Here, in Paper II, we deal with the situation where the number of particles is not sufficient to resolve all scales in turbulent flows and Lagrangian particles with mixing become an approximate model rather than a stochastic framework for solving exact scalar transport equations. We consider sparse-Lagrangian methods that use relatively small numbers of particles compared to the number of Eulerian grid points and discuss similarities and differences with conventional large eddy simulations—filtered density function (LES-FDF) methods. Special attention is paid to multiple mapping conditioning (MMC) formulation for sparse-Lagrangian simulations. Physical and simulated equations for joint FDFs of reactive scalars are compared and analyzed. The efficiency of the MMC-LES approach that was demonstrated in several recent publications is explained from a methodological perspective.