bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparing two 38-kHz scientific echosounders
Authors: Jech J. Michael , Foote Kenneth G. , Chu Dezhang , Hufnagle Lawrence C.
Published: December 2006

The EK500 has been the state-of-the-art scientific echosounder for surveying marine fish stocks for over a decade; the EK60 is its successor. Ensuring comparability in performance is vital during the transition from the EK500 to the EK60. To quantify the respective performances, each echosounder was calibrated in tandem by the standard-target method using the same 38-kHz, 12° beam width, split-beam transducer, with alternating pinging by means of an external triggering-and-switching system. The principal measurements comprised split-beam-determined angle and target strength, on-axis sensitivity, and directionality in the plane normal to the acoustic axis, as measured with a 60-mm-diameter copper sphere. Ambient noise, including volumetric reverberation, was also measured. Principal comparisons included those of the time-series and histograms of split-beam-determined target strength; respective alongship and athwartship angles as determined by the split-beam system; and as expected, difference in the split-beam-determined and experimental target-strength values in the plane normal to the acoustic axis. The mean absolute difference in off-axis angle values was also compared. While the performance of the two echosounders is generally similar, systematic differences exist. For the particular calibration measurements, the time variability in measurements of on-axis target strength was of the order of 1 dB for the EK500 and 2 dB for the EK60. The target-strength distribution for measurements made with the EK500 was normal, with standard deviation 0.2–0.3 dB, whereas for the EK60, the target-strength distribution was distinctly skewed and the standard deviation varied over 0.3–0.5 dB. Differences were found between the split-beam and physical-angle measurements. They were noticeably larger in the case of the EK60. Differences in performance between the two echosounders suggest refinements to the new system that will help realize its full potential in scientific work.
Rothschild–Stiglitz's definition of increasing risk and the relationship between volatility and risk premium
Authors: Kanniainen Juho
Published: December 2006

This paper analyzes the relationship between volatility and risk premium under the capital asset pricing model and Rothschild and Stiglitz's [Rothschild, M. and J.E. Stiglitz. (1970) Increasing risk I: a definition. Journal of Economic Theory, 2, 225–243.] definition of increasing risk. Especially examined are the conditions of the widely used assumption of constant correlation, which results in a linear relationship. Though both the above model and definition are widely known and accepted, their compatibility has remained unclear in the literature. According to this paper, they are in harmony with the linear relationship, if the correlation between a stock and the market portfolio is less than 0.7. Otherwise a conflict may arise.
Human Gongylonema infection in Iran
Authors: Molavi G.H. , Massoud J. , Gutierrez Y.
Published: December 2006

The first human infection with Gongylonema in Iran is reported in a 35-year-old Iranian woman with complaints of one year duration and treated as a psychotic patient. Two worms, a male, and a female, were retrieved, described, and identified as G. pulchrum based on their morphological characteristics.
The life cycle of Haplorchis pumilio (Trematoda: Heterophyidae) from the Indian region
Authors: Umadevi K. , Madhavi R.
Published: December 2006

The life cycle of the heterophyid fluke, Haplorchis pumilio is elucidated for the first time from the Indian region. Various stages in the life cycle were established based on observations made on natural infections found in snails and fish in a freshwater stream at Visakhapatnam, India and experimental infections carried out in the laboratory. The thiarid snail, Thiara tuberculata served as the first intermediate host and a wide range of freshwater fish as second intermediate hosts. Natural infections with adult flukes were found in the piscivorous birds Ardeola grayii and Bubulcus ibis. Adults were raised experimentally in day-old chicks. Distinguishing features of the cercaria of H. pumilio are: a large body size (200–224×92–96 μm), body–tail ratio of 1:2.1 and densely distributed pigment granules in the parenchyma imparting a brownish tinge to the body. Natural infections with metacercariae were found in the freshwater fish Channa punctatus, C. orientalis, Puntius sophore, Gambusia affinis and fingerlings of Cyprinus carpio and Liza macrolepis. Additionally, experimental infections were established in Therapon jarbua, Esomus danricus and Oreochromis mossambica. Metacercariae were embedded in the caudal muscles of fish and heavy infections induced mortality. Metacercariae were infective at about 15 days of age.
Morphological observations and the effects of artificial digestive fluids on the survival of Diploscapter coronata from a Japanese patient
Authors: Morimoto N. , Korenaga M. , Yagyu K. , Kagei N. , Fujieda M. , Bain O. , Wakiguchi H. , Hashiguchi Y. , Sugiura T.
Published: December 2006

Unusual non-human parasitic nematodes and eggs were detected in the faeces of an 8-year-old Japanese female suffering from Henoch-Schönlein purpura. The worms were adult female rhabditiform nematodes measuring 325.6–441.2 μm in length and 18.3–26.5 μm in width. One pair of the labia oris was notched with many spiny projections, while the other pair was strongly curved outwards. The worms were identified using light and scanning electron microscopy as the free-living nematode Diploscapter coronata (Cobb) based on their characteristic morphology. The patient's faeces containing worms and eggs were cultured using a filter-paper culture technique and after 7 days of culture, male as well as female worms were recovered. Worm survival time and hatchability of the eggs were examined in vitro after treatment with an artificial gastric or intestinal fluid. Although adult worms survived for less than one minute, eggs hatched after treatment with artificial gastric fluid. This suggests that eggs accidentally ingested or produced by adult D. coronata could develop in the human gastro-intestinal tract. Some morphological features of male D. coronata are also described.
Where in Europe should we look for sources of the cutaneous trematode Collyriclum faba infections in migrating birds?
Authors: Sitko J. , Sitko J.
Published: December 2006

Cutaneous cysts with trematodes of Collyriclum faba have been found in birds during their spring and post-breeding migrations in the Czech Republic. During spring migrations, C. faba was found in one dunnock Prunella modularis, two European robins Erithacus rubecula, three common nightingales Luscinia megarhynchos, one song thrush Turdus philomelos and one great reed warbler Acrocephalus arundinaceus. During post-breeding migration, the same parasite was found in one garden warbler Sylvia borin, one whitehroat S. communis, three goldcrests Regulus regulus and one Eurasian treecreeper Certhia familiaris. The newly identified hosts of C. faba are dunnock, common nightingale, song thrush, great reed warbler and Eurasian treecreeper. Geographical areas of the birds' infection were identified from an analysis of reports on ringed birds of the same species, the time necessary for the development of cutaneous cysts with C. faba and the time of their survival, and hitherto known geographical areas of endemic occurrence of C. faba. It is presumed that birds trapped during spring migrations were infected in some montane and submontane regions in south-western Europe (the Alps, the Apennines). Birds infected during autumn migration or post-breeding vagrancy could have been infected in the Central European Carpathians, the region of C. faba endemic occurrence. For migrating birds, the impact of C. faba infections has not been hitherto assessed.
Morphological variability within Oesophagostomum bifurcum among different primate species from Ghana
Authors: de Gruijter J.M. , Blotkamp J. , Gasser R.B. , Amponsah S. , Polderman A.M.
Published: December 2006

Adult Oesophagostomum bifurcum (Nematoda: Strongylida) from human and non-human primates from Ghana were compared in order to investigate the extent of morphological variability within the species. Using analysis of variance and principal component analysis, significant differences in morphological characters (such as parasite length, width, length of the oesophagus and length of spicules) were demonstrated between O. bifurcum worms from humans, the Mona, Patas or Green monkey and/or Olive baboons. These findings suggest that O. bifurcum from different species of primate host represent distinct population variants, also supported by recent epidemiological and genetic studies of O. bifurcum from such hosts.
Diagnostic value of IgG isotype responses against Brugia malayi antifilarial antibodies in the clinical spectrum of brugian filariasis
Authors: Wongkamchai S. , Rochjanawatsiriroj C. , Monkong N. , Nochot H. , Loymek S. , Jiraamornnimit C. , Hunnangkul S. , Choochote W.
Published: December 2006

To study the diagnostic significance of antifilarial IgG subclasses in the clinical spectrum of brugian filariasis, IgG1, IgG3 and IgG4 antifilarial antibodies were determined in an exposed population comprising 74 asymptomatic amicrofilaraemics, 30 microfilaraemics, 20 lymphangitis and 16 elephantiasis patients resident in Narathiwart province, an area endemic for Brugia malayi lymphatic filariasis in southern Thailand. The dominant isotype of antifilarial antibody was IgG4. A significantly higher percentage of individuals were positive for IgG1 in the microfilaraemic and lymphangitis groups compared with the elephantiasis and endemic normal patients, while a significantly higher positive rate of IgG3 was found in those with lymphangitis. The possible role of these isotypes for diagnostic purposes and the pattern of antibody response in various clinically manifesting groups are discussed.
Eosinophil cationic protein, specific IgE and IgG4 in human toxocariasis
Authors: Magnaval J.-F. , Faufingue J.-H. , Morassin B. , Fabre R.
Published: December 2006

Among 67 French patients presenting a toxocaral infection, various demographic, environmental, clinical and laboratory parameters (blood eosinophil count, eosinophil cationic protein (ECP), serum total IgE, specific IgE against common inhalant allergens, specific IgE and IgG4 against Toxocara excretory-secretory antigens) were investigated. Correlation studies and logistic regression analyses were conducted, testing elevated levels of ECP, specific anti-Toxocara IgE or IgG4 as outcome variables An elevated ECP level was significantly associated with both cough and rhinitis, a high level of specific anti-Toxocara IgE with itchy rashes and possible atopic status, and an increase of specific anti-Toxocara IgG4 with rural residence.
The effect of the hookworm Ancylostoma ceylanicum on the mucosal architecture of the small intestine in hamsters
Authors: Alkazmi L.M.M. , Dehlawi M.S. , Behnke J.M.
Published: December 2006

Hookworms are known to cause marked changes to the intestinal mucosa, especially in relation to erosion of the villi. However, since the development of enteropathy has not been examined thoroughly through quantitative experiments on infected animals, the results of experiments conducted in hamsters infected with Ancylostoma ceylanicum are reported. Changes to intestinal architecture were first apparent between 12 and 14 days after infection, and then increased in intensity for 3–4 weeks, persisting for as long as worms were present (>63 days). Following infection, the height of villi declined from a mean of 1002 μm in naïve controls to less than 200 μm and as low as 18 μm in one case. The depth of the crypts of Lieberkuhn increased from a baseline value of 166 μm in naïve controls to in excess of 600 μm within 6 weeks of infection. Mitotic figures had a baseline value of 5.5 per villus-crypt unit, and this rose to in excess of 25 in some experiments. Changes were dependent on the intensity of the parasite burden on day 20, but by 30 days after infection changes in all three values were maximal and density-dependent relationships were no longer clearly apparent. Villus height and crypt depth returned to near normal values within a week of the removal of worms, although group means for both remained different from naïve controls for at least 3 weeks after treatment. Cellular division, as reflected in numbers of mitotic figures, stayed elevated for over 5 weeks after removal of worms. The results suggest that enteropathy in hookworm infections stems from a combination of intestinal immune responses and from the grazing activities of the adult worms on the mucosal surface, but is not sufficient per se for expulsion of this parasite.
CAUDELLA BIPOLARIS SP. NOV. (MICROTHYRIACEAE) ON BREDEMEYERA FLORIBUNDA (POLYGALACEAE) FROM THE BRAZILIAN CERRADO
Authors: PEREIRA O. L. , FILARDI F. L. R.
Published: December 2006

Caudella bipolaris sp. nov. (Microthyriaceae), found on leaves of the liana Bredemeyera floribunda Willd. (Polygalaceae) from the Brazilian cerrado, is described and illustrated. This is the fourth known Caudella species and the first reported on a member of the family Polygalaceae. Unique within the genus are the species' bipolar ascospore appendages.
OLD WORLD GESNERIACEAE XII: FURTHER MISCELLANEOUS SPECIES OF CYRTANDRA IN BORNEO
Authors: HILLIARD O. M. , BURTT B. L.
Published: December 2006

Nineteen miscellaneous species of Bornean Cyrtandra are dealt with. Cyrtandra atrichoides, C. congestiflora, C. crockerella, C. dulitiana, C. kanae, C. libauensis, C. plicata, C. vaginata and C. disparoides subsp. inconspicua are newly described. Descriptions and discussion are provided for C. erythrotricha and C. poulsenii, originally published with diagnoses only. Cyrtandra axillaris, C. longicarpa and C. microcarpa are also described, while C. borneensis, C. dajakorum, C. glomeruliflora, C. latens and C. prolata are reduced to synonymy.
A NEW SPECIES OF DRYPETES (PUTRANJIVACEAE) FROM THE CENTRAL AFRICAN REPUBLIC
Authors: HARRIS D. J . , WORTLEY A. H.
Published: December 2006

The new species Drypetes bakembei D.J.Harris & Wortley (Putranjivaceae), from tropical forest in the south west Central African Republic, is described and illustrated.
Modeling Shear Damage to Suspended CHO Cells during Cross‐Flow Filtration
Authors: Vickroy Bruce , Lorenz Karen , Kelly William
Published: December 2006

A mathematical model is presented for predicting the shear‐induced decrease in live cells occurring over time during tangential flow filtration. The model uses a cell death rate constant ( K) and considers the effects of flow rate, solution viability, and filtration system volumes and dimensions. Single pass and recycle capillary experiments with solutions of high (93%), medium (87%), and low (70%) viability were run, where the maximum laminar shear stress ranged from 10– 300 Pa, to validate the model and determine cell death rate constants. The K values for the suspended CHO cells used in this research ranged from 0.06 to 12.5 s−1. These K values increased with shear stress, as expected, and also as the solution viability decreased.
A Novel Porphyrin‐Based Photocatalytic System for Terpenoids Production from (R)‐(+)‐Limonene
Authors: Trytek Mariusz , Fiedurek Jan , Radzki Stanisław
Published: December 2006

A porphyrin‐based photoexcited system has been revealed to be an efficient catalyst for d‐limonene biotransformation under mild conditions and using molecular oxygen or/and H2O2 as oxidants. The influence of the oxidant, the wavelength of visible light, and the photoexcitation time on the catalytic system were studied for limonene oxidation with 5,10,15,20‐tetraphenylporphyrin (H2TPP) as a catalyst. This porphyrin‐catalyzed oxidation of limonene to three main products identified as carvone, an unknown product with a verbenone‐like mass spectrum (1), and a (1 S,4 R)‐ p‐mentha‐2,8‐diene 1‐hydroperoxide (2). The highest conversion yield of these products was achieved at a very high molar ratio of H2TPP to limonene. The dependence of the biotransformation yield on the kind of solvent with different acceptor/donor electron properties was also investigated. Ethyl alcohol proved to be the best among the considered additives used for the reaction. Limonene photooxidation was not significantly dependent on wavelengths of visible light. It was concluded by UV‐vis experiments that the reaction proceeds via a free‐radical or/and molecular mechanism. Additional evidence for its radical nature was obtained from reactivity investigations. Maximal yield of carvone was obtained in the medium containing 90% of the substrate, within the period of 18 to 36 h of exposition to sunlight.
Toward a Psychophysiology of Expertise
Authors: Amidzic Ognjen , Riehle Hartmut J. , Elbert Thomas
Published: December 2006

Gamma-band activity (GBA) bursts have been viewed as a signature for ignitions in localized Hebbian cell assemblies and are thought to indicate active memory. Using whole-head magnetoencephalography, we recorded focal bursts of GBA during chess playing. Unlike highly skilled chess grandmasters, with amateur chess players focal gamma bursts prevailed in deeper structures in the region of the medial temporal lobes. This observation is consistent with the interpretation of memory formation in amateur chess players. For the frontal and parietal cortex the relationship was reversed, with more frequent gamma bursts found in chess grandmasters, indicating that the retrieval of chunks from expert memory is based on the recruitment of these neocortical areas. The results suggest the possibility that time-dependent reorganization during the formation of expert memory can be studied in humans and support the theory that the medial temporal lobe and hippocampal formation play a transitional role during the creation of expert memory in the neocortex.
First space‐based observations of formic acid (HCOOH): Atmospheric Chemistry Experiment austral spring 2004 and 2005 Southern Hemisphere tropical‐mid‐latitude upper tropospheric measurements
Authors: Rinsland Curtis P. , Boone Chris D. , Bernath Peter F. , Mahieu Emmanuel , Zander Rodolphe , Dufour Gaëlle , Clerbaux Cathy , Turquety Solène , Chiou Linda , McConnell John C. , Neary Lori , Kaminski Jacek W.
Published: December 2006

The first space‐based measurements of upper tropospheric (110–300 hPa) formic acid (HCOOH) are reported from 0.02 cm−1 resolution Atmospheric Chemistry Experiment (ACE) Fourier transform spectrometer solar occultation measurements at 16°S–43°S latitude during late September to early October in 2004 and 2005. A maximum upper tropospheric HCOOH mixing ratio of 3.13 ± 0.02 ppbv (1 ppbv = 10−9 per unit volume), 1 sigma, at 10.5 km altitude was measured during 2004 at 29.97°S latitude and a lower maximum HCOOH mixing ratio of 2.03 ± 0.28 ppbv, at 9.5 km altitude was measured during 2005. Fire counts, back trajectories, and correlations of HCOOH mixing ratios with ACE simultaneous measurements of other fire products confirm the elevated HCOOH mixing ratios originated primarily from tropical fire emissions. A HCOOH emission factor relative to CO of 1.99 ± 1.34 g kg−1 during 2004 in upper tropospheric plumes is inferred from a comparison with lower mixing ratios measured during the same time period assuming HITRAN 2004 spectroscopic parameters.
Concepts and designs of ion implantation equipment for semiconductor processing
Authors: Rose Peter H. , Ryding Geoffrey
Published: December 2006

Manufacturing ion implantation equipment for doping semiconductors has grown into a two billion dollar business. The accelerators developed for nuclear physics research and isotope separation provided the technology from which ion implanters have been developed but the unique requirements of the semiconductor industry defined the evolution of the architecture of these small accelerators. Key elements will be described including ion generation and beam transport systems as well as the techniques used to achieve uniform doping over large wafers. The wafers are processed one at a time or in batches and are moved in and out of the vacuum by automated handling systems. The productivity of an implanter is of economic importance and there is continuing need to increase the usable beam current especially at low energies.
The effects of iron as a dopant on the dielectric properties of ferroelectric potassium tantalate niobate (KTaxNb1−xO3)
Authors: Abdulraheem Yaser M. , Gentile Anthony L. , Stafsudd Oscar M.
Published: December 2006

Presented here is a preliminary study on the effects of iron as a dopant in potassium tantalate niobate (KTaxNb1−xO3) (KTN). Crystals of high purity were grown using a top-seeded isothermal method with starting materials that were purified ensuring that the impurity content was controlled down to less than 10ppm. The study included introducing iron to KTN single crystals of high purity both during crystal growth and through thermal diffusion after growth. Dielectric measurements versus temperature were used to reveal the origins of the ferroelectric phase transition in the KTN:Fe system. Large shifts in the Curie temperature have been shown to be a direct consequence of the presence of iron impurities in KTN. The conventional theories of ferroelectricity do not explain this effect; however, a model is proposed to explain the observed behavior. The model is based on the concept of “polar microregions” proposed previously by Bidault and Maglione [J. Phys. I France 7, 543 (1997)] and others to explain ferroelectricity in potassium tantalate lightly doped with niobium.
Relaxation processes at the glass transition in polyamide 11: From rigidity to viscoelasticity
Authors: Frübing Peter , Kremmer Alexander , Gerhard-Multhaupt Reimund , Spanoudaki Anna , Pissis Polycarpos
Published: December 2006

Relaxation processes associated with the glass transition in nonferroelectric and ferroelectric polyamide (PA) 11 are investigated by means of differential scanning calorimetry, dynamic mechanical analysis, and dielectric relaxation spectroscopy (DRS) in order to obtain information about the molecular mobility within the amorphous phase. In particular, the effects of melt quenching, cold drawing, and annealing just below the melting region are studied with respect to potential possibilities and limitations for improving the piezoelectric and pyroelectric properties of PA 11. A relaxation map is obtained from DRS that shows especially the crossover region where the cooperative α relaxation and the local β relaxation merge into a single high-temperature process. No fundamental difference between quenched, cold-drawn, and annealed films is found, though in the cold-drawn (ferroelectric) film the α relaxation is suppressed and slowed down, but it is at least partly recovered by subsequent annealing. It is concluded that there exists an amorphous phase in all structures, even in the cold-drawn film. The amorphous phase can be more rigid or more viscoelastic depending on preparation. Cold drawing not only leads to crystallization in a ferroelectric form but also to higher rigidity of the remaining amorphous phase. Annealing just below the melting region after cold drawing causes a stronger phase separation between the crystalline phase and a more viscoelastic amorphous phase.
Transport properties of metallic La1−xSrxCoO3 (0.30≤x≤0.50) ferromagnet
Authors: Mandal P. , Hassen A. , Choudhury P.
Published: December 2006

To elucidate the nature of transport mechanism below Curie temperature TC, we have analyzed the temperature dependence of resistivity (ρ) and thermopower (S) of metallic La1−xSrxCoO3 (0.30≤x≤0.50). At low temperature well below TC both ρ and S exhibit T2 behavior whereas over a temperature interval just below TC, they show a T4 dependence due to the scattering of charge carriers by magnetic fluctuations. These fluctuations can be suppressed by a magnetic field, leading to a negative bulk magnetoresistance in cobaltates and in other itinerant ferromagnets such as manganites and CrO2.
Using scaling laws to understand the growth mechanism of atomic layer deposited WNxCy films on methyl-terminated surfaces
Authors: Martin Hoyas A. , Schuhmacher J. , Whelan C. M. , Fernandez Landaluce T. , Vanhaeren D. , Maex K. , Celis J. P.
Published: December 2006

Atomic layer deposition (ALD) of tungsten nitride carbide (WNxCy) on methyl-terminated self-assembled monolayers (SAMs) is investigated. SAM substrates provide extended transient regimes of different lengths, during which the WNxCy film growth is nonlinear. The extent of this offset from linear growth depends on the alkyl chain length. The film morphology is characterized by atomic force microscopy, which reveals island growth and fractal behavior. During the transient regime, WNxCy deposition shows nonconservative growth, as revealed by the low film density and a roughness exponent α of ∼0.4–0.5. During the linear growth regime, a conservative mechanism is observed, characterized by a higher, constant film density and α∼0.7. These observations do not apply to all ALD deposited films. In particular, ALD HfO2 films follow a conservative-type mechanism during the entire range of growth.
Rotationally inelastic scattering of OH (Π3∕22, v=, J=3∕2, f) by HBr (Σ1, v=, J<4)
Authors: Moise A. , Cireasa R. , Parker D. H. , ter Meulen J. J.
Published: December 2006

Relative state-to-state cross sections of OH molecules in the Π3∕22, v=0, J=3∕2, MJ=3∕2, f state have been determined for transitions up to Π3∕22, v=0, J=11∕2, f and Π1∕22, v=0, J=7∕2, e states by collisions with HBr molecules (Σ1, v=0, J<4) at 750cm−1 collision energy. In order to investigate features of the anisotropy of the OH–HBr potential energy surface, the steric asymmetries, which account for the effect of the OH orientation with respect to the collision partner, have been measured. A comparison with other systems previously studied shows strong similarities with the OH–HCl system.
Spin-polarized transport through an Aharonov-Bohm interferometer with Rashba spin-orbit interaction
Authors: Chi Feng , Li Shu-Shen
Published: December 2006

We study electron transport through an Aharonov-Bohm (AB) interferometer with a noninteracting quantum dot in each of its arms. Both a magnetic flux ϕ threading through the AB ring and the Rashba spin-orbit (SO) interaction inside the two dots are taken into account. Due to the existence of the SO interaction, the electrons flowing through different arms of the AB ring will acquire a spin-dependent phase factor in the tunnel-coupling strengths. This phase factor, as well as the influence of the magnetic flux, will induce various interesting interference phenomena. We show that the conductance and the local density of states can become spin polarized by tuning the magnetic flux and the Rashba interaction strength. Under certain circumstances, a pure spin-up or spin-down conductance can be obtained when a spin-unpolarized current is injected from the external leads. Therefore, the electron spin can be manipulated by adjusting the Rashba spin-orbit strength and the structure parameters.
Three-dimensional simulation of laser-produced plasma for extreme ultraviolet lithography applications
Authors: Sizyuk V. , Hassanein A. , Sizyuk T.
Published: December 2006

Laser-produced plasma (LPP) from a tin target is being considered as the light source for the next generation of extreme ultraviolet (EUV) lithography. An integrated model was developed to simulate the plasma behavior and the EUV radiation output in LPP devices. The model includes plasma heat conduction and hydrodynamic processes in a two-temperature approximation, as well as detailed photon radiation transport using Monte Carlo methods. Multiple laser beams incident on a single target have been simulated in full three-dimensional geometry, using the total variation-diminishing scheme for the plasma hydrodynamics and an implicit scheme for heat conduction processes. Numerical simulations showed that EUV conversion efficiency increases for multiple-beam devices with specific optimum laser locations and direction compared to a single-beam device.
Relativistically intense plane electromagnetic waves in electron–positron plasmas: Nonlinear self-modulation and harmonics generation regimes
Authors: Shiryaev O. B.
Published: December 2006

A fully nonlinear one-dimensional problem describing the interactions of relativistically intense plane electromagnetic waves and cold locally non-neutral electron–positron plasmas is derived from Maxwell and fluid dynamics equations. Numerical and asymptotic solutions to this problem for phase velocities close to the speed of light are presented. Depending on the magnitude of the plasma longitudinal electric-field potential, the system considered is found to support two distinct regimes of plane electromagnetic wave propagation: a nonlinear self-modulation one with the coupling of a fast transversely polarized electromagnetic field to a slow longitudinal plasma field, and a harmonics generation one with both of these fields oscillating with comparable frequencies. In the former case, a splitting of the electromagnetic field spectrum into a series of closely located bands occurs, whereas in the latter one the propagating field spectrum is a set of radiation harmonics.
Born-Oppenheimer expansion at constant energy
Authors: Mead C. Alden
Published: December 2006

The well-known Born-Oppenheimer procedure considers molecular properties in the limit of large values of the nuclear mass M (in units of electronic mass), with quantum numbers held constant. It is shown that the lowest-order correction to the molecular wave function is proportional to M−3∕4. Here we consider the same expansion, but with energy held constant instead of quantum numbers. We show that, if the singular coupling term near a conical intersection is removed via a quasidiabatic transformation, the lowest-order remaining correction is proportional to M−1∕2.
The influence of beam energy and oxidation on quantitative carbide analysis in the scanning electron microscope
Authors: Rodenburg C. , Rainforth W. M.
Published: December 2006

In this paper the origin of the carbide/matrix contrast in secondary electron images and its ramifications for spatial resolution are investigated. A profound influence of the backscattered electron yield and the oxidation of the steel matrix was found, which manifests itself in a contrast reversal at low primary electron beam energies. The authors established that low beam energies are necessary to obtain the required spatial resolution. Strategies for optimizing the contrast between carbide and matrix in secondary electron images without compromising the spatial resolution are presented. A simple method to estimate the thickness of thin oxide layers from low voltage secondary electron images is also described.
Effective creation of oxygen vacancies as an electron carrier source in tin-doped indium oxide films by plasma sputtering
Authors: Luo S. N. , Kono A. , Nouchi N. , Shoji F.
Published: December 2006

We have investigated the effect of hydrogen on the resistivity, Hall mobility, and carrier density of ITO films on glass substrates using a low-pressure plasma sputtering method. It was found that a certain hydrogen content in the Ar plasma leads to improvement in the resistivity relating to an increase in the electron carrier density. The improvement is explained by oxide reduction due to the reaction of hydrogen radicals with indium oxide (In2O3). The effect of postannealing on the electrical properties confirmed that the improvement of the resistivity is a result of an increase in oxygen vacancies as the electron carrier source in the ITO film. Oxygen extraction in the initial stages of ITO film growth, due to the glass substrate surface, is suggested to create oxygen vacancies as the electron carrier source for improvement in the resistivity of the films.
Direct observation of negative phase velocity and positive group velocity in time domain for composite right/left-handed transmission lines
Authors: Wang Youzhen , Zhang Yewen , He Li , Liu Fuqiang , Li Hongqiang , Chen Hong
Published: December 2006

We use the time-domain method to directly determine the negative phase velocity and positive group velocity in the composite right/left-handed transmission line (CRLH TL). Within the frequency region of a left-handed passband, the position and time behavior of a Gaussian modulated wave form with a frequency of 1GHz is investigated, and it shows that the phase velocity and group velocity are reversed along the CRLH TL. The experimental results of the time-domain method are compared with the results derived from the dispersion relation obtained using the frequency-domain method. The experimental results of both the time-domain and frequency-domain method agree well with theoretical values.
Epitaxial growth of (SrBa)Nb2O6 thin films on SrTiO3 single crystal substrate
Authors: Infortuna Anna , Muralt Paul , Cantoni Marco , Setter Nava
Published: December 2006

( Sr Ba ) Nb 2 O 6 (SBN) thin films with tetragonal tungsten bronze structure were deposited on strontium titanate single crystals by pulsed laser deposition. Epitaxial relations were studied as a function of substrate termination and orientation. On STO(100) surface, SrO termination leads to (001) SBN orientation, whereas TiO2 termination to (310) orientation. A growth model is proposed, explaining the epitaxial relation with the substrate on the basis of the perovskite kernel contained in the unit cell of the tetragonal tungsten bronze structure. The perovskite kernel grows in cube-on-cube relation on the perovskite substrate. The high growth temperature of at least 720°C assures the necessary mobility for the arriving atoms to organize in the SBN structure around the perovskite nuclei. Piezoelectric measurements carried out by atomic force microscopy on individual grains show that it is possible to switch the polarization, thus proving ferroelectric properties. The geometry of the piezoelectric response is compatible with grain orientation as known from diffraction experiments.
Hopping conduction in boron doped amorphous carbon films
Authors: Vishwakarma P. N. , Subramanyam S. V.
Published: December 2006

The electrical transport properties of boron doped graphitelike amorphous carbon films have been studied. Variable range hopping (VRH) conduction is found to be the conduction mechanism in these carbon films. The conduction in high temperature regime follows the Mott VRH [J. Non-Cryst. Solids 1, 1 (1968)], whereas a crossover from the Mott [Electronic Process in Non-crystalline Materials (Clarendon, Oxford, 1971)] to the Efros-Shklovskii [J. Phys. C 8, L49 (1975)] VRH is observed at low temperatures. Additional support to this transition is evident from negative magnetoresistance in VRH regime when the sample is deep inside the insulating side of the metal insulator transition. Various calculated parameters such as localization length, density of states at the Fermi level, and Coulomb gap for insulating samples have been estimated from the experimental data. The density of states at the Fermi level shows a gradual shift with a corresponding variation in boron doping level, indicating a change in the density of conducting π electrons due to substitutional doping of boron in the carbon network.
Equilibrium and eigenfunctions estimates in the semiclassical regime
Authors: Camus Brice
Published: December 2006

We establish eigenfunctions estimates, in the semiclassical regime, for critical energy levels associated to an isolated singularity. For Schrödinger operators, the asymptotic repartition of eigenvectors is the same as in the regular case, excepted in dimension one where a concentration at the critical point occurs. This principle extends to pseudo-differential operators and the limit measure is the Liouville measure as long as the singularity remains integrable.
Evolution of an expanding dusty plasma with negative ions
Authors: Kechouri B. , Djebli M.
Published: December 2006

The dusty plasma radial expansion is studied in the case of a spherical as well as cylindrical configuration. The effect of negative ions is introduced through the dust charge fluctuation equation. Electrons, positive, and negative ions are modelled by the Boltzmann distribution function and the dust grains by fluid equations. Using the self-similar theory, the nonlinear set of differential equations is solved numerically. It is found that the dust charge presents a critical value which depends on the negative ion species type. It is also found that the dust expansion ends earlier and the lighter particle densities profiles depend on the dust initial charge.
Effect of the adsorbate stiffness on the resonance response of microcantilever sensors
Authors: Tamayo Javier , Ramos Daniel , Mertens Johan , Calleja Montserrat
Published: December 2006

The authors present a theoretical model to predict the resonance frequency shift due to molecule adsorption on micro- and nanocantilevers. They calculate the frequency shift experienced by cantilevers made of either silicon or the polymer SU-8, when two adsorbates, myosin protein and an alkanethiol, are attached to the cantilever surface. They demonstrate that the effect of the adsorbate stiffness can be comparable or even larger than the mass effect, producing positive frequency shifts. The results provide methods for decoupling both opposite effects and routes for the design of resonators with high sensitivity to molecule adsorption based on either stiffness or mass effects.
Spectroscopy of atomic and molecular defects in solid He4 using optical, microwave, radio frequency, and static magnetic and electric fields (Review)
Authors: Moroshkin P. , Hofer A. , Ulzega S. , Weis A.
Published: December 2006

A little more than a decade ago our team extended the field of defect spectroscopy in cryocrystals to solid He4 matrices, in both their body-centered cubic (bcc) and hexagonal close-packed (hcp) configurations. In this review paper we survey our pioneering activities in the field and compare our results to those obtained in the related fields of doped superfluid helium and doped helium nanodroplets, domains developed in parallel to our own efforts. We present experimental details of the sample preparation and the different spectroscopic techniques. Experimental results of purely optical spectroscopic studies in atoms, exciplexes, and dimers and their interpretation in terms of the so-called bubble model will be discussed. A large part of the paper is devoted to optically detected magnetic resonance (ODMR) processes in alkali atoms. The quantum nature of the helium matrix and the highly isotropic shape of the local trapping sites in the bcc phase make solid helium crystals ideal matrices for high-resolution spin physics experiments. We have investigated the matrix effects on both Zeeman and hyperfine magnetic resonance transitions and used ODMR to measure the forbidden electric tensor polarizability in the ground state of cesium. Several unexpected changes of the optical and spin properties during the bcc-hcp phase transition can be explained in terms of small bubble deformations.
Nonlinear and shock waves in superfluid He II
Authors: Kolmakov G. V. , Efimov V. B. , Ganshin A. N. , McClintock P. V. E. , Lebedeva E. V. , Mezhov-Deglin L. P.
Published: December 2006

We review studies of the generation and propagation of nonlinear and shock sound waves in He II (the superfluid phase of He4), both under the saturated vapor pressure (SVP) and at elevated pressures. The evolution in shape of second and first sound waves excited by a pulsed heater has been investigated for increasing power W of the heat pulse. It has been found that, by increasing the pressure P from SVP up to 25atm, the temperature Tα, at which the nonlinearity coefficient α of second sound reverses its sign, is decreased from 1.88to1.58K. Thus at all pressures there exists a wide temperature range below Tλ where α is negative, so that the temperature discontinuity (shock front) should be formed at the center of a propagating bipolar pulse of second sound. Numerical estimates show that, with rising pressure, the amplitude ratio of linear first and second sound waves generated by the heater at small W should increase significantly. This effect has allowed us to observe at P=13.3atm a linear wave of heating (rarefaction) in first sound, and its transformation to a shock wave of cooling (compression). Measurements made at high W for pressures above and below the critical pressure in He II, Pcr=2.2atm, suggest that the main reason for initiation of the first sound compression wave is strong thermal expansion of a layer of He I (the normal phase) created at the heater-He II interface when W exceeds a critical value. Experiments with nonlinear second sound waves in a high-quality resonator show that, when the driving amplitude of the second sound is sufficiently high, multiple harmonics of second sound waves are generated over a wide range of frequencies due to nonlinearity. At sufficiently high frequencies the nonlinear transfer of the wave energy to sequentially higher wave numbers is terminated by the viscous damping of the waves.
Infrared study of high-pressure molecular phases of carbon dioxide
Authors: Giordano V. M. , Gorelli F. A. , Bini R.
Published: December 2006

The infrared absorption spectra of the high-pressure crystalline phases II, III, and IV of solid CO2 were studied by using a resistively heated diamond anvil cell up to 30GPa. The employment of crystal slabs having thickness of ∼2μm allowed the study of the strongly absorbing fundamental bending and antisymmetric stretching modes without saturation. These are the first data for phases II and IV in the fundamental modes spectral region; furthermore the high sample quality allowed an improved characterization of the infrared spectra of phases I and III as compared with previous studies. A comparison of the spectral structure and of the frequency evolution with pressure of the crystal modes between phase I and the higher-pressure phases clearly indicates the close resemblance among all these phases. In particular, the dramatic change of the intermolecular interaction claimed for phases II (dimeric association) and IV (large molecular bending) can be ruled out and, as a consequence, the hypothesis of a transition from the molecular phase I to the silica-like phase V through intermediate nonmolecular phases can be discarded.
Temperature dependence of the magnetic susceptibility of solid oxygen
Authors: Jeżowski A. , Litwicki Z. , Sumarokov V. V. , Stachowiak P.
Published: December 2006

The temperature dependence of the magnetic susceptibility of polycrystalline oxygen samples is measured in the range from 1to54K. The measurements are performed using our home-designed SQUID-based gradiometer. The sensitivity of the instrument with respect to susceptibility reaches values of the order of 10−13. The results are compared with data in the literature.
On the possible reason for enhanced superconductivity in multiwall carbon nanotubes
Authors: Gaididei Yu. B. , Loktev V. M.
Published: December 2006

Based on the structural peculiarity of two-layer graphene, which consists of translational and energetic nonequivalency of carbon atoms from different sublattices, it is shown that the density of long-wave electronic states at the Fermi level is finite (in contrast to the graphene monolayer). It is suggested that may be the reason why the critical temperature of the superconducting transition in multiwall nanotubes is more than ten times higher than in single-wall nanotubes.
Higher-order Föppl models of steady wake flows
Authors: Protas Bartosz
Published: December 2006

In this paper we construct two-dimensional steady potential flows past a circular cylinder as generalizations of the point-vortex Föppl system. For a given classical Föppl system, these higher-order systems form a two-parameter family depending on the truncation order N and the area A of the vortex region desingularizing the original Föppl solution. We characterize the higher-order equilibria analytically and numerically, and show that their modified linear stability properties make the higher-order systems useful models for a class of flow control problems.
Versatile cluster based photoelectron spectrometer
Authors: Knappenberger K. L. , Jones C. E. , Sobhy M. A. , Castleman A. W.
Published: December 2006

A recently constructed cluster based photoelectron spectrometer is described. This instrumentation is unique in that it enables the kinetic energy analysis of electrons ejected from both anions and neutral clusters. This capability permits the investigation of discrete electronic levels in all charge states (anionic, neutral, and cationic). A laser vaporization plasma reactor cluster source affixed with a sublimation cell is employed to produce a variety of metal clusters, and the resulting cluster distributions are analyzed with time-of-flight mass spectrometry. The corresponding electronic structure is analyzed with a “magnetic bottle” photoelectron spectrometer. Examples of instrument performance operating in both anion photodetachment and neutral multiphoton ionization (MPI) modes are provided. In the case of neutral MPI, the corresponding product distribution is collected with a Wiley-McLaren [Rev. Sci. Instrum. 26, 1150 (1955)] mass spectrometer mounted perpendicular to the magnetic bottle photoelectron spectrometer.
Crystal cleavage mechanism for UHV scanning tunneling microscopy
Authors: Oreshkin A. I. , Muzychenko D. A. , Radchenko I. V. , Mancevich V. N. , Panov V. I. , Oreshkin S. I.
Published: December 2006

A device for UHV cleavage of crystal specimens for the use with scanning tunneling microscopy (STM) has been suggested and developed. We present a device suitable for the precise cleavage of semiconductors. The device needs only small space and can be easily mounted in a small and compact UHV chamber equipped with a wobble-stick manipulator. In order to prove the technique, UHV STM measurements on InAs(110) surfaces with different bulk conductivities (p and n types) have been performed.
Advantages of NiOx electrode over Au in low-voltage tetracene-based phototransistors
Authors: Choi Jeong-M. , Lee Kimoon , Hwang D. K. , Kim Jae Hoon , Im Seongil , Park Ji Hoon , Kim Eugene
Published: December 2006

We report on the tetracene-based photo-thin-film transistors (photo-TFTs) which adopt thin poly-4-vinylphenol (PVP)/aluminum oxide (AlOx) bilayer for a gate dielectric and two different source/drain (S∕D) electrodes: semitransparent NiOx and Au. Our tetracene-based TFT with NiOx S∕D electrode exhibited quite good field effect mobility (μ=∼0.23cm2∕Vs), high on/off current ratio (Ion∕Ioff) of ∼105, and good photo-to-dark current ratio (Iph∕Idark=∼104) under an ultraviolet (364nm) illumination while that with Au S∕D electrodes showed much lower device performance (μ=∼0.08cm2∕Vs, Ion∕Ioff=∼104, and Iph∕Idark=∼20), although the both TFTs operated at a low voltage of −8V. With the hole-injection and light-reception advantages of NiOx electrode, our tetracene photo-TFT demonstrated good dynamic optical gating.
Transport properties of Co-doped β-FeSi2 single crystals
Authors: Arushanov E. , Lisunov K. G. , Vinzelberg H. , Behr G. , Schumann J.
Published: December 2006

Resistivity ρ(T) of Co-doped n-type FeSi2 single crystals is investigated in the temperature range of 4.2K⩽T⩽300K, and analyzed within the framework of different hopping conductivity models according to the relation ρ(T)=ApT1∕pexp[(T0∕T)1∕p]. Both the Mott regime with p=4 [Metal-Insulator Transitions (Taylor & Francis, London, 1990)] and the Shklovskii-Efros regime with p=2 [Electronic Properties of Doped Semiconductors (Springer, Berlin, 1984)] within the variable-range hopping conductivity are observed, as well as a crossover of them, where the temperature dependence of the resistivity follows a scaling law ln(ρ∕ρ0)=Af(T∕Tx). The values of the characteristic (T0) and transition temperatures and the width of the soft Coulomb gap in the spectrum of the density of the localized states (DOS) Δ≈0.5–1.6meV are determined. In addition to Δ, our results suggest existence of the rigid gap in the spectrum of the DOS with the value up to δ≈0.35meV. The rigid gap is consistent with a polaronic nature of the charge carriers in the investigated compound.