bluuebunny/crossref_metadata_2025 huggingface dataset:
Interfacial profiles of miscible poly(4‐trimethylsilylstyrene)/polyisoprene bilayer films
Authors: Harada Masashi , Suzuki Takahisa , Ohya Masayuki , Kawaguchi Daisuke , Takano Atsushi , Matsushita Yushu , Torikai Naoya
Published: April 2005

Compositional profiles of bilayer films in the direction normal to the interfaces have been investigated by neutron reflectivity measurements and analyzed with mean field theory. The bilayer films were prepared with poly(4‐trimethylsilylstyrene) (PTMSS) and polyisoprene (PI), which constitute a miscible polymer pair and whose blends show phase separation at the lower critical solution temperature (LCST) by heating. Because we can accurately control the degree of polymerization of component polymers and can adjust the Flory–Huggins interaction parameter, χ, with the temperature, T, according to the relationship χ = 0.027–9.5/T, the phase behavior and the interfacial structure of PTMSS and PI are predictable by mean field theory. When the bilayer films of PTMSS and PI were set at 90 °C, which is a temperature below the LCST, diffusion at the interface was observed, and the original interface disappeared in several hours; this supports the idea that the polymer pair is miscible. No clear interfaces were identified below the LCST, whereas broad interfaces, compared with that of the strong segregation pairs, were observed above the LCST. The compositions of each layer are consistent with that of the coexisting phase in the polymer blends, and the interfacial widths agree well with the theoretical prediction considering the effect of capillary waves. In addition, all annealed films have a thin surface layer of PTMSS corresponding to surface segregation induced by the lower surface energy of PTMSS (with respect to that of PI). Thus, the interfacial profiles of PTMSS/PI bilayer films have been totally prospected in the framework of mean field theory. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1486–1494, 2005
Photochemical control of photoluminescence property of photoactive polythiophenes
Authors: Zhao Xiongyan , Niu Yuhuan , Hu Xiao
Published: April 2005

Azobenzene‐functionalized polythiophene derivatives, Poly[4‐((4‐(phenyl)azo)phenoxy)alkyl‐3‐thienylacetate] (alkyl=hexyl and octyl) (P6 and P8) and the copolymers of 3‐hexylthiophene and 4‐((4‐(phenyl)azo)phenoxy)alkyl‐3‐thienylacetate (alkyl=hexyl and octyl) (P66 and P86) were synthesized. The composition, structure, and thermal property of these polythiophene derivatives were fully characterized by NMR, FTIR, GPC, MDSC, and XRD. The structural dependence of the photochromic features and thermochromic behaviors were also investigated by means of photoluminescence and UV‐Vis absorption spectroscopy. The results have shown that the azobenzene substitution renders the homopolymer (P6 and P8) some interesting optical properties that can be modulated by UV light irradiation. In these azobenzene‐modified polythiophenes, the intensity of photoluminescent emission associated with the conjugated polythiophene main chain was found to decrease significantly upon UV irradiation. The finding suggests that the photo‐induced trans–cis isomerization of the azobenzene pendant groups has significant effect on photoluminescent emission. However, the effect becomes less prominent for copolymer P66 and P86 due to the lower content of azobenzene chromophore in the side chain of the copolymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1421–1432, 2005
Characterization of Plasma‐Polymerized Fused Polycyclic Compounds for Binding Conducting Polymers
Authors: Winther‐Jensen Bjørn , Norrman Kion , Kingshott Peter , West Keld
Published: April 2005

Summary: An investigation is made of the plasma polymerization of fused polycyclic monomers containing a dioxy‐ring that is fused to an aromatic ring. These molecules provide the basis for very efficient polymerization mechanisms in which only the dioxy‐ring undergoes ring opening during the polymerization with the remaining part of the monomer remaining intact. XPS, ToF‐SIMS, and IR are used to investigate the chemistry of the films produced by plasma polymerization of EDT, which contains a high content of the aromatic group. We find that the plasma‐polymerized films of EDT contain intact thiophene groups with hydrogen in the α position which is able to “co‐polymerize” with thiophene derivatives polymerized by conventional oxidative polymerization, thereby forming a conducting thiophene polymer bonded to the substrate. The durability of the surface modification procedure is demonstrated by micropatterning of PEDT by a lithographic lift‐off technique, where line‐widths down to 1.25 μm are obtained.

Microscope picture of a micropattern in poly(3,4‐ethylenedioxythiophene); line width 2.5 μm.

magnified image

Microscope picture of a micropattern in poly(3,4‐ethylenedioxythiophene); line width 2.5 μm.
Adaptation ofSaccharomyces cerevisiaeto high hydrostatic pressure causing growth inhibition
Authors: Iwahashi Hitoshi , Odani Mine , Ishidou Emi , Kitagawa Emiko
Published: April 2005

Genome‐wide mRNA expression profiles ofSaccharomyces cerevisiaegrowing under hydrostatic pressure were characterized. We selected a hydrostatic pressure of 30 MPa at 25 °C because yeast cells were able to grow under these conditions, while cell size and complexity were increased after decompression. Functional characterization of pressure‐induced genes suggests that genes involved in protein metabolism and membrane metabolism were induced. The response to 30 MPa was significantly different from that observed under lethal conditions because protein degradation was not activated under 30 MPa pressure. Strongly induced genes those that contribute to membrane metabolism and which are also induced by detergents, oils, and membrane stabilizers.
Effects of lipid kinase expression and cellular stimuli on phosphatidylinositol 5‐phosphate levels in mammalian cell lines
Authors: Roberts Hilary F. , Clarke Jonathan H. , Letcher Andrew J. , Irvine Robin F. , Hinchliffe Katherine A.
Published: April 2005

Phosphatidylinositol 5‐phosphate (PtdIns5P) is a relatively recently discovered inositol lipid whose metabolism and functions are not yet clearly understood. We have transfected cells with a number of enzymes that are potentially implicated in the synthesis or metabolism of PtdIns5P, or subjected cells to a variety of stimuli, and then measured cellular PtdIns5P levels by a specific mass assay. Stable or transient overexpression of Type IIα PtdInsP kinase, or transient overexpression of Type Iα or IIβ PtdInsP kinases caused no significant change in cellular PtdIns5P levels. Similarly, subjecting cells to oxidative stress or EGF stimulation had no significant effect on PtdIns5P, but stimulation of HeLa cells with a phosphoinositide‐specific PLC‐coupled agonist, histamine, caused a 40% decrease within 1 min. Our data question the degree to which inositide kinases regulate PtdIns5P levels in cells, and we discuss the possibility that a significant part of both the synthesis and removal of this lipid may be regulated by phosphatases and possibly phospholipases.
Peroxiredoxin‐I is an autoimmunogenic tumor antigen in non‐small cell lung cancer
Authors: Chang Jong Wook , Lee Seung Hee , Jeong Ju Yeon , Chae Ho Zoon , Kim Young Chul , Park Zee-Yong , Yoo Yung Joon
Published: April 2005

In eukaryotic cells, peroxiredoxins are both antioxidants and regulators of H2O2‐mediated signaling. We previously found that peroxiredoxin‐I (Prx‐I) was overexpressed in non‐small cell lung cancer (NSCLC) tissue. Since overexpressed protein can induce a humoral immune response, we examined whether serum from NSCLC patients exhibited immunoreactivity against Prx‐I using Western blotting. We found that 25 (47%) of 53 NSCLC patients tested had autoantibodies against Prx‐I in their sera, whereas such activity was detected in 4 (8%) sera from 50 healthy subjects. Prx‐I itself was detected in the sera from 18 (34%) of 53 NSCLC patients but in only 1 (2%) serum from 50 controls. Moreover, 17% of NSCLC sera were positive to both Prx‐I antibody and antigen but none in control sera. The data indicate both Prx‐I autoantibody and circulating antigen are potential biomarkers for use in serological diagnosis of NSCLC. Interestingly enough, we found that Prx‐I was secreted by lung adenocarcinoma cells (A549) but not by non‐cancer lung cells (BEAS 2B) or breast cancer cells (MCF7). This cell culture study suggests the possibility of Prx‐I secretion from NSCLC tumor tissues.
Multiple myelomas in cats
Authors: Hanna Fikry
Published: April 2005

Multiple myelomas are uncommon neoplasms of the bone marrow of cats [Weber NA, Tebeau CS (1998) An unusual presentation of multiple myeloma in two cats. Journal of the American Animal Hospital Association34 (6), 477–483]. Nine cats diagnosed with multiple myelomas were retrospectively identified over a 16-year period (1986–2002). Cats with multiple myelomas were older than 7 years (mean age 11.7 years); six males and three females were affected (2.1), but no breed predisposition was evident. Treatment of multiple myelomas consisted of supportive management in the nine cats and anti-neoplastic therapy in eight cats. Supportive treatment consisted of maintaining hydration, renal function and antimicrobial therapy even when there was no sign of infection. Anti-neoplastic therapy with melphalan and prednisolone was carried out in eight cats. Three failed to respond to treatment and five responded to treatment, but the response was only partial and temporary in one cat. The five cats that responded were improved clinically and had reduced serum protein levels. Five out of eight cats (63%) responded to chemotherapy, and it appeared to be complete in four cats and partial in one cat. Survival time in those cats was 15, 4, 17 and 24 months.
DIVERSITY IN FAMILY PLANNING USE AMONG ETHNIC GROUPS IN GUATEMALA
Authors: DE BROE SOFIE , HINDE ANDREW , MATTHEWS ZOË , PADMADAS SABU S.
Published: April 2005

This study investigates the ethnic differentials in contraceptive use in the north-eastern Ch’orti area of Guatemala, a region dominated by the Ladino culture. Data come from a household survey and in-depth interviews with service providers carried out in 2001 in the town of Jocotán, and a survey carried out in 1994 in two nearby indigenous villages (aldeas). Descriptive analysis and logistic regression are used to explore the data. Previous DHS surveys have used dress and language to classify ethnic groups. In this paper, an alternative approach based on self-identification is adopted. The results reveal significant differences in contraceptive behaviour among different ethnic groups within the same town and region. The results show that self-identified Ladino women who represented the minority of the population had contraceptive behaviour similar to their counterparts elsewhere in Latin America. The extremely low levels of contraceptive use among indigenous women from the aldeas suggest that the corresponding DHS figures in this region are probably overestimated.
The development of Malaysia's position on Antarctica: 1982 to 2004
Authors: Tepper Rohan , Haward Marcus
Published: April 2005

This paper examines the development of Malaysia's position on the ‘Question of Antarctica’ and its relationship to the Antarctic Treaty System (ATS). Malaysia's challenges to, and criticisms of, the Antarctic Treaty Consultative Parties (ATCPs) are mapped from 1982 to 2004, indicating a shift from challenging the ATS to engagement with the ATCPs. The paper highlights how Malaysia's position on the ‘Question of Antarctica’ reflected a mix between domestic political concerns and its international and regional interests. The mix between domestic and international interests is reflected in the ongoing involvement of Malaysian Prime Minister Mahathir bin Mohamad, including his retirement in 2003, in shaping Malaysia's position, from initiating the challenge to the ATS in 1982 to recommending that Malaysia join the ATS in 2004. Mahathir's domestic agenda, most notably through Malaysia's ‘Vision 2020’ development program is identified as providing an impetus for change, increasing Malaysian scientific interest in Antarctica and the Southern Ocean.
An evaluation of distance sampling to estimate badger (Meles meles) abundance
Authors: Hounsome T. D. , Young R. P. , Davison J. , Yarnell R. W. , Trewby I. D. , Garnett B. T. , Delahay R. J. , Wilson G. J.
Published: April 2005

Distance sampling is a common and increasingly used method of estimating animal abundance in conservation and management programmes. The precision of a distance sampling survey can be estimated from the field data, but accuracy can only be evaluated by comparison with the true population size. For wild mammal populations, such opportunities are rare. The high‐density badger Meles meles population at Woodchester Park in Gloucestershire, U.K. has been routinely and intensively live‐trapped for the past 30 years. The estimates of abundance based on mark–recapture analyses of the live‐trapping data provided a reliable baseline against which to evaluate distance sampling for a badger population. A distance sampling survey was carried out in autumn 2002 by using spotlighting along line transects. Owing to the impractical nature of spotlighting in closed habitats, such as woodland, surveys were conducted in open habitat only. A radio‐tracking study provided behavioural data that were used to estimate the proportion of the population available for sampling in open habitats. This was incorporated as a multiplier into the DISTANCE analysis. The estimate of abundance from distance sampling was 76 badgers (% CV=42.2), using a multiplier based on radio‐tracking data from autumn only. When the multiplier was derived from radio‐tracking data from across the whole year, based on a larger sample of tracked badgers, the distance sampling abundance estimate was 77 badgers (% CV=25.9). These compared favourably to the mark–recapture estimate of 68 badgers (% C.V=7.4). The lack of precision in the distance sampling density estimate was largely owing to the inclusion of the multiplier. Distance sampling combined with data on habitat use can produce reliable estimates of badger abundance in areas of medium to high density, particularly in landscapes of primarily open habitat.
A unique seasonal pattern in phytoplankton biomass in low‐latitude waters in the South China Sea
Authors: Tseng Chun‐Mao , Wong George T. F. , Lin I.‐I. , Wu C.‐R. , Liu K.‐K.
Published: April 2005

A distinctive seasonal pattern in phytoplankton biomass was observed at the South East Asian Time‐series Study (SEATS) station (18°N, 116°E) in the northern South China Sea (SCS). Surface chlorophyll‐a, depth‐integrated chlorophyll‐a and primary production were elevated to 0.3 mg/m3, ∼35 mg/m2 and 300 mg‐C/m2/d, respectively, in the winter but stayed low, at ≤0.1 mg/m3, ∼15 mg/m2 and 110 mg‐C/m2/d as commonly found in other low latitude waters, in the rest of the year. Concomitantly, soluble reactive phosphate and nitrate+nitrite in the mixed layer also became readily detectable in the winter. The elevation of phytoplankton biomass coincided approximately with the lowest sea surface temperature and the highest wind speed in the year. Only the combined effect of convective overturn by surface cooling and wind‐induced mixing could have enhanced vertical mixing sufficiently to make the nutrients in the upper nutricline available for photosynthetic activities and accounted for the higher biomass in the winter.
Decreased surface salinity in the Sea of Okhotsk during the last glacial period estimated from alkenones
Authors: Seki Osamu , Kawamura Kimitaka , Sakamoto Tatsuhiko , Ikehara Minoru , Nakatsuka Takeshi , Wakatsuchi Masaaki
Published: April 2005

Studies of sediment cores from the Sea of Okhotsk, which is characterized by seasonal sea ice, have shown a large variability of sea ice indicators during the glacial‐interglacial cycles. In this study, we apply the relative abundance of the C37:4 alkenone to total C37 alkenones (%C37:4) as a molecular indicator of salinity and water masses to further investigate surface oceanographic condition in the Sea of Okhotsk in the glacial period. We found a large fluctuation of %C37:4 (4–35%) with higher values (20∼35%) during the last glacial period and lower values (<8%) during warm periods, suggesting a decreased surface salinity in the glacial period. The variation of %C37:4 was found to be consistent with the ice rafted debris (IRD) in the sediment core (correlation coefficient (r2) between %C37:4 and IRD: 0.72). This suggests that the duration of seasonal sea ice was longer in the glacial period than today. The lowered surface salinity in the glacial might also have been seriously affected by the close‐off of the shallow Soya Strait, which currently transports massive volumes of saline water from the Sea of Japan to the Sea of Okhotsk.
Intraseasonal Kelvin waves along the southern coast of Sumatra and Java
Authors: Iskandar Iskhaq , Mardiansyah Wijaya , Masumoto Yukio , Yamagata Toshio
Published: April 2005

The intraseasonal sea level variations along the southern coast of Sumatra and Java are investigated using in situ data and the TOPEX/Poseidon satellite altimetry data. The analysis shows that there are two intraseasonal variations of distinct timescale: 20–40 days during boreal summer (JJA) and 60–90 days during boreal winter (DJF). During boreal summer the shorter time variations of the sea level along the coast of Sumatra and Java are traced back to the eastern equatorial Indian Ocean (EIO); this indicates the importance of the remotely forced equatorial Kelvin waves. During boreal winter, on the other hand, both the remote winds over the EIO and the local alongshore winds are important in explaining the longer time variations of the sea level along the coast. Further analysis indicates that these intraseasonal variations are associated with the coastal Kelvin waves with phase speed ranging from 1.5 to 2.86 m/s. A simple analytical model forced by daily wind stress confirms the above intraseasonal variations along the southern coast of Sumatra and Java.
Understanding the long‐term variability of African dust transport across the Atlantic as recorded in both Barbados surface concentrations and large‐scale Total Ozone Mapping Spectrometer (TOMS) optical thickness
Authors: Chiapello Isabelle , Moulin Cyril , Prospero Joseph M.
Published: April 2005

The interannual variability of African dust transport over the north tropical Atlantic is monitored using in situ surface concentrations measurements performed at Barbados since 1966, along with the Total Ozone Mapping Spectrometer (TOMS) and Meteosat dust optical thickness (DOT) records covering the last two decades. Despite their differences in spatial coverage, the two dust records are in good agreement at both monthly and annual timescales over the 22 years of common operation. This demonstrates that the Barbados dust record is representative of the year‐to‐year variability of dust export over the north tropical Atlantic during both winter and summer. The satellite DOT are used to assess the characteristics of the impact of climate factors, i.e., North Atlantic Oscillation (NAO) and Sahel drought, on dust emission and export as a function of season, and in terms of spatial extend of their influence. The analysis shows a large regional impact of Sahel drought on dust emissions and transport both in winter and in summer, whereas the influence of the NAO dominates the winter export and is more geographically limited to the eastern Atlantic north of 15°N, and possibly some localized source regions (southern Mauritania and the Bodele depression). Overall, the combination of the 35 years of Barbados measurements of African dust with 22 years of satellite dust survey over the Atlantic highlights very high dust loads in the mid‐1980s related to the severe Sahel drought (maximum impact in 1983) and persistently high dusty conditions in the 1990s, most probably due to the continuation of relatively dry conditions in Sahel in the recent years.
Role of magnetic polarons in transport properties of EuB6
Authors: Yu Unjong , Chatterjee Jayita , Min B. I.
Published: April 2005

In order to understand the anomalous magnetic and transport properties of a low carrier density magnetic system EuB6, the magnetic polaron model has been explored with the strong interaction between charge carriers and local magnetic moments. The role of lattice degrees of freedom and the localization effect due to impurity are also studied through the mean-field approximation and the Monte Carlo method incorporating the exact diagonalization. It has been shown that the metal-insulator transition near magnetic transition in EuB6 is naturally understandable in the framework of the magnetic polaron model.
Electric, thermal, and magnetic properties of CeSix with 1.57<x⩽2.0
Authors: Smith Jesse S. , Zan J. A. , Lin C. L. , Li Jing
Published: April 2005

It has been shown that CeSix exhibits a variety of interesting physical properties, however the magnetic ground state was unclear due to the possible coexistence of multiple magnetic phases. In this study, the physical properties of CeSix with 1.57<x⩽2.0 have been investigated to clarify the magnetic ordering ground states throughout the series. For Si concentrations greater than 1.80, samples are paramagnetic. Ferromagnetic ordering first appears when Si concentration is decreased to 1.80. For Si concentrations ranging from 1.73 to 1.80, TC=13.8K. As Si concentration is further decreased below 1.73, TC steps down to 12K, remaining constant down to the lowest concentration studied, x=1.57. Interestingly, the latter change in magnetic ground state is accompanied by a structural distortion from the ThSi2-type tetragonal structure to the GdSi2-type orthorhombic phase. In the magnetic regime, zero-field-cooled and field-cooled magnetization data are irreversible, indicating a strong domain-wall pinning effect. Values of TC are corroborated by specific-heat and resistivity measurements.
Structural, electronic, and magnetic properties of Sr2−xBaxFeMoO6(⩽x⩽2)
Authors: Habib A. H. , Saleem A. , Tomy C. V. , Bahadur D.
Published: April 2005

Here we report on the investigation of structural, transport, and magnetic properties in double perovskite system, Sr2−xBaxFeMoO6(0⩽x⩽2). X-ray Diffraction analysis shows that the compounds form in single phase across the whole solid solution range. The Rietveld refinement of the x-ray data clearly indicates a structural transition from tetragonal (I4∕m) for x⩽0.6 to cubic (Fm3m) for x⩾1.6 with an orthorhombic (Fmmm) structure in the intermediate region (0.8⩽x⩽1.4). Magnetization studies show a regular increase in saturation magnetization from 2.0μB∕f.u.(x=0) to 3.0μB∕f.u.(x=2) with increasing Ba concentration. However, magnetization as well as electron-spin resonance (ESR) measurements confirmed a systematic decrease in the Curie temperatures from 420 K (x=0) to 310 K (x=2) with increasing x. Resistivity measurements carried out in zero magnetic field and for a field of 0.8 T reveal appreciably higher magnetoresistance for intermediate compositions in comparison to those at the ends.
Investigation of magnetic interactions in Ba2EuRu1−xCuxO6 using magnetization and Eu151 Mössbauer studies
Authors: Kumar Rakesh , Tomy C. V. , Paulose P. L. , Nagarajan R.
Published: April 2005

We report here the magnetization and Eu151 Mössbauer studies in ordered perovskite-type oxides, Ba2EuRu1−xCuxO6 (x=0.0, 0.1 and 0.2). The parent compound, Ba2EuRuO6, shows a magnetic ordering at 40K. Both the magnetization and Mössbauer measurements indicate that the magnetic ordering temperature is unchanged as Cu partially substitutes Ru. Despite the fact that the ground state of Eu3+ is a nonmagnetic J=0 state, the Eu151 Mössbauer resonance spectrum shows a clear splitting into six lines for T<TN, indicating a large magnetic hyperfine field (∼280kOe). This large hyperfine field may be arising due to a strong exchange field between the ordered Ru moments acting on the Eu3+ ions, inducing a magnetic moment for the Eu3+ ions.
The extent of quantum critical fluctuations into the heavy-fermion phase: A neutron scattering study of Ce(Ru1−xFex)2Ge2
Authors: Montfrooij W. , Aronson M. C. , Rainford B. D. , Mydosh J. A. , Hendrikx R. , Gortenmuller T. , Murani A. P. , Haen P. , Swainson I.
Published: April 2005

We present inelastic neutron scattering measurements on the heavy-fermion compound Ce(Ru1−xFex)2Ge2 (x=0.87). This composition is close to the quantum critical point (QCP) compound (x=0.76) in which it was observed that the decay of spin fluctuations could no longer be described by a simple exponential in time. Here we show that the relaxation mechanism for spin fluctuations exhibits a qualitatively similar momentum and temperature dependence in both compositions, possibly reflecting the underlying scaling law at the QCP. However, the details of the relaxation mechanism demonstrate that critical fluctuations are strongly damped along the composition axis.
Field dependence of the magnon dispersion in the Kondo lattice CeCu2 up to 12T
Authors: Schedler R. , Witte U. , Rotter M. , Loewenhaupt M. , Schmidt W.
Published: April 2005

Ce Cu 2 can be classified as a Kondo lattice which shows antiferromagnetic (AF) order below TN=3.5K [R. Trump et al., J. Appl. Phys. 69, 4699 (1991)]. The orthorhombic crystal and the simple AF magnetic structure with two magnetic moments in the primitive unit cell requires two magnon modes which are observed in zero and low magnetic fields and well described by spin wave theory. However, at higher fields, at and above 3T, an unexpected, additional magnetic excitation is observed. In contrast to the two low-energy magnon modes, it exhibits a steeper (factor 2) field dependence and a flat dispersion. Its origin is unclear.
Perpendicular interface resistance in Co∕NbxTi1−x multilayers for normal and superconducting NbTi alloy with x=0.4, 0.6
Authors: Huang S. Y. , Lee S. F. , Huang J. C. , Hwang G. H. , Yao Y. D.
Published: April 2005

We report here the resistance of Co∕NbxTi1−x multilayers, for x=0.4 and 0.6, with current flowing perpendicular to the layer plane at 4.2K. When NbTi films are sandwiched between Co, we found that there are critical thicknesses of 20nm for x=0.4 and 27nm for x=0.6, below which no superconducting transition could be found. Using a series resistor model, we extracted the unit area resistance of one pair of Co∕NbTi interfaces and compared with the pure Nb case we have reported. The influence of mean free paths and superconducting coherence lengths is analyzed.
Revival of superconductivity by Y3+∕Ca2+ substitution in YBa2Cu2.7Co0.3O7 without reported phase transformation
Authors: Ansari M. A. , Nigam Rashmi , Awana V. P. S. , Gupta Anurag , Saxena R. B. , Kishan H. , Lalla N. P. , Ganesan V. , Narlikar A. V. , Cardoso C. A.
Published: April 2005

Results of phase formation, resistivity (ρ), and thermoelectric power (S), are reported on Y1−xCaxBa2Cu2.7Co0.3O7 compounds with x=0.1 and 0.2. Pristine compound, i.e., without Co or Ca substitution crystallizes in orthorhombic structure with space-group P∕mmm. The Cu-site Co substituted compound, i.e., YBa2Cu2.7Co0.3O7 is tetragonal. With simultaneous doping of Ca at the Y site in Co substituted compound, i.e., Y1−xCaxBa2Cu2.7Co0.3O7 the tetragonal nature still remains. ρ(T) measurements showed superconducting transition temperature (Tc) to decrease from 90K (YBa2Cu3O7) to 33K for YBa2Cu2.7Co0.3O7, which with further Ca substitution increases from 33to53K (Y0.9Ca0.1Ba2Cu2.7Co0.3O7) and 67K for Y0.8Ca0.2Ba2Cu2.7Co0.3O7. Tc decreases first with Cu-site Co substitution by hole filling and later recovers by simultaneous hole creation by Y site Ca substitution. Room temperature thermoelectric power S (300K), which is an indirect measure of mobile carriers shows the decrease of carriers with Co doping and creation by Ca substitution. Our results demonstrate the hole filling by Co substitution is compensated by simultaneous Ca substitution.
Magnetism of A2Cu2Mo3O12 (A=Rb or Cs): Model compounds of a one-dimensional spin-1∕2 Heisenberg system with ferromagnetic first-nearest-neighbor and antiferromagnetic second-nearest-neighbor interactions
Authors: Hase Masashi , Ozawa Kiyoshi , Suzuki Osamu , Kitazawa Hideaki , Kido Giyuu , Kuroe Haruhiko , Sekine Tomoyuki
Published: April 2005

Magnetic susceptibility and magnetization showed that A2Cu2Mo3O12 (A=Rb or Cs) includes a one-dimensional spin-1∕2 Heisenberg system with ferromagnetic first-nearest-neighbor (1NN) and antiferromagnetic second-nearest-neighbor (2NN) competing exchange interactions (competing system). Values of the 1NN and 2NN interactions are estimated as J1=−138K and J2=51K for A=Rb or J1=−93K and J2=33K for A=Cs. Rb2Cu2Mo3O12 is a suitable compound to study the competing system with ferromagnetic J1, because other interactions are small. The value of J2∕J1 indicates that Rb2Cu2Mo3O12 has a spin-singlet incommensurate ground state.
Theoretical study of the magnetic ordering in rare-earth compounds with face-centered-cubic structure
Authors: Duan Chun-gang , Sabiryanov R. F. , Liu Jianjun , Mei W. N. , Dowben P. A. , Hardy J. R.
Published: April 2005

We present a detailed theoretical study of the magnetic ordering in heavy rare-earth compounds with a face-centered-cubic structure. In addition to the exchange interactions which are counted up to the third nearest neighbors, the effect of the dipolar interactions and magnetic anisotropic effect are also included in our model Hamiltonian. The interactions parameters are obtained from first-principles band-structure calculations by fitting the total energies of different magnetic configurations to the Heisenberg Model. Thus from utilizing the Monte Carlo simulations, we explained the formation of different magnetic structures in the rare-earth compounds.
Improvement of critical current density and thermally assisted individual vortex depinning in pulsed-laser-deposited YBa2Cu3O7−δ thin films on SrTiO3 (100) substrate with surface modification by Ag nanodots
Authors: Li A. H. , Liu H. K. , Ionescu M. , Wang X. L. , Dou S. X. , Collings E. W. , Sumption M. D. , Bhatia M. , Lin Z. W. , Zhu J. G.
Published: April 2005

Y Ba 2 Cu 3 O 7 films were fabricated by pulsed laser deposition on SrTiO3 (100) single-crystal substrates whose surfaces were modified by the introduction of Ag nanodots. The critical current density (Jc) was found to increase with the number of Ag shots. Zero-field magnetic Jc0 at 77K increased from 8×105 up to 3.5×106A∕cm2 as the number of Ag shots increased from 0 to over 150 times. Microstructure investigations indicated that the crystallinity and the ab alignment gradually improved as the number of Ag nanodots increased. Thermally activated depinning of individual vortices is suggested responsible for a field-independent Jc plateau.
Transport properties of the spinel superconductor CuRh2S4 under pressure
Authors: Ito M. , Kurisaki H. , Nakamura F. , Fujita T. , Suzuki T. , Hori J. , Okada H. , Fujii H.
Published: April 2005

We have carried out the specific heat and electric resistivity measurements of the chalcogenide-spinel compound CuRh2S4 under the hydrostatic pressures up to 8.0GPa, and found out the pressure induced superconductor-insulator (SI) transition at PSI in between 5.0 and 5.6GPa. The value of superconducting transition temperature Tc, which is 4.7K at ambient pressure, increases up to 6.4K at 4.0GPa and turns to decrease with pressurization. With further pressurization, the abrupt loss of Tc occurs at PSI and the system becomes an insulator.
Magnetite: Raman study of the high-pressure and low-temperature effects
Authors: Gasparov L. V. , Arenas D. , Choi K.-Y. , Güntherodt G. , Berger H. , Forro L. , Margaritondo G. , Struzhkin V. V. , Hemley R.
Published: April 2005

We report the results of a low-temperature (300K–15K) high-pressure (up to 22GPa) Raman study of the Verwey transition in magnetite (Fe3O4). We use additional Raman modes observed below the Verwey transition to determine how the transition temperature changes with the quasihydrostatic pressure. Increase of the pressure results in the linear decrease of the Verwey transition temperature, with no discontinuity. The corresponding pressure coefficient dTV∕dP is found to be −5.16±1.19K∕GPa. Such a decrease is substantially larger than the one predicted by the mean-field Coulomb interaction model of the transition.
Evolution from insulator (x=0.003) to metal (x=1) of the Eu2+ local environment in Ca1−xEuxB6
Authors: Urbano R. R. , Pagliuso P. G. , Rettori C. , Schlottmann P. , Nakatsuji S. , Fisk Z. , Sarrao J. L. , Bianchi A. , Oseroff S. B.
Published: April 2005

The local environment of Eu2+ (4f7, S=7∕2) in Ca1−xEuxB6(0.003⩽x⩽1.00) is studied by means of electron spin resonance (ESR). For x≲0.07 the resonances have Lorentzian line shape, indicating an insulating environment for the Eu2+ ions. For x≳0.07, the lines broaden and become Dysonian in shape, suggesting a change to metallic environment for the Eu2+ ions, anticipating the semimetallic character of EuB6. The broadening is attributed to a spin-flip scattering relaxation process due to the exchange interaction between conduction and Eu2+4f electrons. High field ESR measurements for x≳0.30 reveal narrower and anisotropic linewidths, which are attributed to magnetic polarons and Fermi surface effects, respectively.
Effect of conformal roughness on ferromagnetic resonance linewidth in thin Permalloy films
Authors: Maranville B. B. , Mallett J. , Moffat T. P. , McMichael R. D. , Chen A. P. , Egelhoff W. F.
Published: April 2005

The ferromagnetic resonance linewidth is a result of both intrinsic damping and contributions from inhomogeneities, which in thin films can be dominated by the roughness. Microstructural measurements and magnetization dynamics are reported here for 50-nm films of Permalloy deposited on substrates with controlled roughness. Ferromagnetic resonance measurements reveal a strong linewidth broadening that peaks when the magnetization is approximately 30° from the in-plane direction. These results are compared with a recently developed two-magnon theory of resonance broadening due to inhomogeneous demagnetizing fields in a rough film.
Magnetic ordering in single-crystalline SrLaFeO4 and Sr1.1La0.9FeO4
Authors: Jung M. H. , Alsmadi A. M. , Chang S. , Fitzsimmons M. R. , Zhao Y. , Lacerda A. H. , Kawanaka H. , El-Khatib S. , Nakotte H.
Published: April 2005

We report on the magnetic properties of single-crystalline SrLaFeO4 and Sr1.1La0.9FeO4. Both compounds crystallize in the tetragonal K2NiF4 structure (I4∕mmm) with the La and Sr atoms randomly distributed over the 4e crystallographic sites of this structure. SrLaFeO4 orders antiferromagnetically below 350K, and Sr1.1La0.9FeO4, orders antiferromagnetically at about 150K. Both compounds exhibit magnetic structures described by orthorhombic Cmca-type symmetry and two magnetic propagation vectors q1=(12,12,0) and q2=(−12,12,0), representing the two possible magnetic domains. A collinear antiferromagnetic arrangement of the Fe3+ moments confined to the tetragonal basal plane is found. Bulk magnetic studies on SrLaFeO4 show that the properties of this compound are highly anisotropic, and there is evidence for additional magnetic transitions at lower temperatures (30 and 90K). Low-temperature neutron diffraction data were taken to gain some insight into the nature of these transitions.
Interlayer dipolar interactions in multilayered granular films
Authors: Kakazei G. N. , Pogorelov Yu. G. , Costa M. D. , Golub V. O. , Sousa J. B. , Freitas P. P. , Cardoso S. , Wigen P. E.
Published: April 2005

Using the ferromagnetic resonance (FMR) technique, the interlayer coupling is studied in granular multilayered system (CoFe∕Al2O3)n with varying number of layers n=1,…,8. The main difference between the cases of n=1 and n⩾3 is a notable splitting of FMR line under external field normal to layers. This is explained by an interlayer dipolar coupling, only possible for discontinuous layers. The relative magnitudes of two absorption peaks and distance between them are described by a simple model of planar square lattices of magnetic dipoles.
Propagation of an electromagnetic wave in an absorbing anisotropic medium and infrared transmission spectroscopy of liquid crystals
Authors: Scaife B. K. P. , Vij J. K.
Published: April 2005

The theory of absorbance is developed for the entire electromagnetic spectrum of radiation in a semi-infinite anisotropic medium with a second rank dielectric tensor, the elements of which are complex and frequency dependent. The theory of the absorbance A(ω,θ) of an optically anisotropic liquid in an infrared (IR) test cell is then outlined and applied to IR transmission experiments. A formula for the dependence of A(ω,θ), on θ (θ being the angle between the electric vector and the principal optical axis) is derived from first principles. The formula, for radiation of angular frequency ω, viz, A(ω,θ)=−log10[10−A(ω,0)cos2θ+10−A(ω,π∕2)sin2θ] is in agreement with that proposed by Jang, Park, Maclennan, Kim, and Clark [Ferroelectrics 180, 213 (1996) ] and confirms some of the work of Kocot, Wrzalik, and Vij [Liq. Cryst. 21, 147 (1996)]. The comments on this formula by Jang, Park, Kim, Glaser, and Clark [Phys. Rev. E 62, 5027 (2000)], and by Kocot et al. are discussed. The absorbance A(ω,0) and A(ω,π∕2) have been expressed in terms of the optical properties of the material and the dimensions of the cell.
Study of intermolecular interactions in liquid nitrobenzene by depolarized hyper-Rayleigh scattering
Authors: Chen J. , Wong K. Y.
Published: April 2005

We employed depolarized hyper-Rayleigh scattering (HRS) to investigate the intermolecular interactions in liquid nitrobenzene. By comparing the depolarization ratios of the second-harmonic scattered light from neat nitrobenzene and mixtures of nitrobenzene and methanol of varying mixing ratios, we demonstrated the existence of a coherent component of HRS in liquid nitrobenzene. The coherent component was found to essentially disappear at a sufficiently high dilution of the nitrobenzene liquid. We also observed that both localized orientational correlation and delocalized libron excitation contribute to coherent HRS in liquid nitrobenzene. The delocalized contribution to coherent HRS was found to diminish much more readily with the introduction of interstitial foreign molecules than the localized contribution.
Pattern formation in nonextensive thermodynamics: Selection criterion based on the Renyi entropy production
Authors: Cybulski Olgierd , Matysiak Daniel , Babin Volodymyr , Holyst Robert
Published: April 2005

We analyze a system of two different types of Brownian particles confined in a cubic box with periodic boundary conditions. Particles of different types annihilate when they come into close contact. The annihilation rate is matched by the birth rate, thus the total number of each kind of particles is conserved. When in a stationary state, the system is divided by an interface into two subregions, each occupied by one type of particles. All possible stationary states correspond to the Laplacian eigenfunctions. We show that the system evolves towards those stationary distributions of particles which minimize the Renyi entropy production. In all cases, the Renyi entropy production decreases monotonically during the evolution despite the fact that the topology and geometry of the interface exhibit abrupt and violent changes.
Structure and ultrafast dynamics of liquid water: A quantum mechanics/molecular mechanics molecular dynamics simulations study
Authors: Xenides Demetrios , Randolf Bernhard R. , Rode Bernd M.
Published: April 2005

A quantum mechanics/molecular mechanics molecular dynamics simulation was performed for liquid water to investigate structural and dynamical properties of this peculiar liquid. The most important region containing a central reference molecule and all nearest surrounding molecules (first coordination shell) was treated by Hartree–Fock (HF), post-Hartree–Fock [second-order Møller–Plesset perturbation theory (MP2)], and hybrid density functional B3LYP [Becke's three parameter functional (B3) with the correlation functional of Lee, Yang, and Parr (LYP)] methods. In addition, another HF-level simulation (2HF) included the full second coordination shell. Site to site interactions between oxygen-oxygen, oxygen-hydrogen, and hydrogen-hydrogen atoms of all ab initio methods were compared to experimental data. The absence of a second peak and the appearance of a shoulder instead in the gO–O graph obtained from the 2HF simulation is notable, as this feature has been observed so far only for pressurized or heated water. Dynamical data show that the 2HF procedure compensates some of the deficiency of the HF one-shell simulation, reducing the difference between correlated (MP2) and HF results. B3LYP apparently leads to too rigid structures and thus to an artificial slow down of the dynamics.
The photodynamics of ethylene: A surface-hopping study on structural aspects
Authors: Barbatti M. , Ruckenbauer M. , Lischka H.
Published: April 2005

Simulations of the photodynamics of ethylene were carried out by employing the semiempirical direct trajectory with surface hopping method in order to assess quantitatively the importance of different regions of the S2∕S1 and S1∕S0 crossing seams. The results show that during the first 50 fs after a vertical photoexcitation to the ππ* state, the nonadiabatic coupling between the S1 and the S2 states produces a recurrence pattern of oscillation of the populations in these states. Within the first 100 fs, the S1 state population spans a limited region of the configuration space between the initial geometries and the twisted-pyramidalized minimum on the crossing seam (MXS). Depending on the way of counting, about 50% of the S1→S0 transitions occur in the pyramidalized region of the crossing seam, but not necessarily close to the MXS. The remaining 50% occurs in the H-migration and ethylidene regions. Our analysis shows that the ethylidene region becomes more important in later stages of the dynamics when the flux of trajectories that was not effectively converted to the ground state in the pyramidalized region starts to reach this part of the configuration space. The excited-state nonadiabatic dynamics could be employed to generate suitable initial phase space distributions for the hot-ethylene ground-state kinetic studies.
A new mechanism for electron spin echo envelope modulation
Authors: Morton John J. L. , Tyryshkin Alexei M. , Ardavan Arzhang , Porfyrakis Kyriakos , Lyon S. A. , Briggs G. Andrew D.
Published: April 2005

Electron spin echo envelope modulation (ESEEM) has been observed for the first time from a coupled heterospin pair of electron and nucleus in liquid solution. Previously, modulation effects in spin-echo experiments have only been described in liquid solutions for a coupled pair of homonuclear spins in nuclear magnetic resonance or a pair of resonant electron spins in electron paramagnetic resonance. We observe low-frequency ESEEM (26 and 52kHz) due to a new mechanism present for any electron spin with S>1∕2 that is hyperfine coupled to a nuclear spin. In our case these are electron spin (S=3∕2) and nuclear spin (I=1) in the endohedral fullerene N@C60. The modulation is shown to arise from second-order effects in the isotropic hyperfine coupling of an electron and N14 nucleus.
Efficient operating mode of the plasma wakefield accelerator
Authors: Lotov K. V.
Published: April 2005

A new operating mode of the plasma wakefield accelerator is found at which high efficiency of the driver-to-witness energy exchange can be achieved simultaneously with high transformer ratio and low energy spread. The efficient acceleration is realized in the blowout regime with a high-current moderate-length driver, if most of the driver and the whole witness are inside the cavern, and the beams are shaped to flatten the profile of the longitudinal electric field. The efficient regime can be demonstrated with state-of-the-art electron beams, but requires a longitudinal compression of the drive beam, high density plasma, and precise control of driver and witness shapes.
Nonlinear local piezoelectric deformation in ferroelectric thin films studied by scanning force microscopy
Authors: Shvartsman V. V. , Pertsev N. A. , Herrero J. M. , Zaldo C. , Kholkin A. L.
Published: April 2005

Local piezoelectric deformation is investigated in (Pb,La)TiO3 (PLT) and Pb(Zr,Ti)O3 (PZT) thin films via scanning force microscopy (SFM) as a function of the ac voltage Vac applied between the conducting tip and the bottom electrode. Thus obtained voltage dependence of the effective piezoelectric coefficient (local piezoelectric nonlinearity) is compared with the corresponding macroscopic piezoelectric behavior determined by laser interferometry. As expected, the local piezoresponse of PLT films measured inside uniformly polarized areas (ferroelectric domains) remains almost linear with increasing Vac until the driving voltage becomes comparable with the coercive one. The corresponding macroscopic response is substantially nonlinear, suggesting significant contribution from the motion of 90° domain walls. On the contrary, in PZT films the local piezoelectric behavior is strongly nonlinear, whereas the macroscopic piezoelectric coefficient is almost field independent. Moreover, depending on the polarity of probed as-grown domains, the local piezocoefficient of PZT films is found to display either enhancement or reduction with increasing ac voltage. The “positive” domains (i.e., domains having polarization vector pointing to the film-free surface) are often unstable with increasing Vac and switch into the opposite polarization state under an ac voltage several times smaller than that required for global polarization reversal. This effect is explained by the presence of charged domain boundaries below the surface and their local depinning induced by external field. It is envisaged that SFM can be used not only for polarization mapping of ferroelectric surfaces but also as a probe for studying local polarization profiles beneath the SFM tip.
Third-order nonlinearities of Bi12GeO20 crystal measured by nanosecond radiation
Authors: Ganeev R. A. , Ryasnyansky A. I. , Palpant B. , Debrus S.
Published: April 2005

Negative nonlinear refraction is observed in the photorefractive crystal Bi12GeO20 (BGO) using 7-ns, 532-nm pulsed radiation. The nonlinear refractive index of BGO is measured to be γ=−3.8×10−13cm2W−1 using the z-scan technique. The self-defocusing of nanosecond pulses is attributed to the appearance of free carriers generated from defects, donors, and interband transitions. The nonlinear losses caused by two-photon absorption and self-scattering from dynamic grating are discussed. The nonlinear absorption coefficient is measured to be β=3.8×10−8cmW−1. Moreover, a variation of γ and β with intensity is observed. The comparison with self-focusing and two-photon absorption previously measured using 55-ps pulses is discussed.
Effects of finite sized charge on downstream wake patterns
Authors: Bose Anirban , Janaki M. S.
Published: April 2005

Finite sized charged particles introduced into streaming dusty plasmas produce wake patterns in the downstream region. The structure of the wake potential is found to depend on values of the charge size and Mach number M, where M is the ratio of the flow speed to the dust acoustic speed.
Intensity-dependent equivalent circuit parameters of organic solar cells based on pentacene and C60
Authors: Yoo Seunghyup , Domercq Benoit , Kippelen Bernard
Published: April 2005

We present studies of the current–voltage characteristics of organic solar cells based on heterojunctions of pentacene and C60 as a function of illumination intensity. The photovoltaic response at a given illumination level is parameterized and modeled using the equivalent circuit model developed for inorganic pn-junction solar cells. Reduction in shunt resistance and increase in diode reverse saturation current density are observed upon increase of the light intensity. We demonstrate that this effect can be modeled by a refined equivalent circuit model that contains an additional shunt resistance and an additional diode the properties of which are functions of the light intensity. The effects of these additional components on the overall photovoltaic performance are discussed.