bluuebunny/crossref_metadata_2025 huggingface dataset:
Macrodynamic feedback interaction between trade and production
Authors: Eitelberg Eduard
Published: October 2006

Some significant aspects of dynamic behaviour of price level and economic activity are directly related to macroeconomic interaction between trade and production feedback loops. It is shown how this simple interaction can give, and likely has given, rise to macroeconomic business cycles as well as to counter‐intuitively slow responses to disturbances or commands. It is suggested that many puzzling deviations from economic equilibrium are caused by nonlinear interaction between feedback loops with independent regulators in macro‐ and microeconomy. Copyright © 2006 John Wiley & Sons, Ltd.
A benchmarking framework for methods to design flexible business processes
Authors: Daoudi Feriel , Nurcan Selmin
Published: October 2006

The assumption made in this article is that flexible processes require specific design methods. The choice of a method for modelling flexible processes depends on many criteria and situations that we gathered in a benchmarking framework. The user can use it as a decision support tool to choose the appropriate method in order to design flexible business processes in a given project situation. This framework also includes managerial concerns such as the time and the budget of the project. We use three enterprise modelling techniques to illustrate how to use the proposed framework. Copyright © 2006 John Wiley & Sons, Ltd.
The desirability function in evaluation of the response of phytoplankton communities to toxicants
Authors: Kaitala Seppo , Maximov Viktor N.
Published: October 2006

The response of phytoplankton communities to copper, cadmium, zinc, and pentachlorophenolate in 24‐factorial experiments were investigated. Seven experiments lasting from three to five days were carried out. During each experiment, 16 bottles were incubated in situ. Different species had different responses to the toxicants. For evaluation of the response of the whole community the desirability function was used. The densities of abundant species in the control bottle were used as a reference and considered as desirable. All exceptions more than one standard deviation from the control were considered detrimental. The value of the overall desirability function D was calculated as a geometrical mean of the values of the desirability function for n single species

D = (d1d2…dn)1/n.

The overall desirability function values in the factorial experiments were treated by regression analyses. In all experiments, the responses of the phytoplankton community to the toxicants were similar. In general, copper caused the greatest change in phytoplankton communities.
Micromethod for acute aquatic toxicity assessment using the green alga selenastrum capricornutum
Authors: Blaise C. R.
Published: October 2006

The method is intended for use (a) as a screening test to estimate toxicity to phytoplankton and (b) as part of an integrated scheme for hazard assessment of waters and wastewaters.
A direct resazurin test for measuring chemical toxicity
Authors: Thomsom K. , Liu D. , Kaiser K. L. E.
Published: October 2006

A rapid, simple, and inexpensive biochemical test for use in the mass screening of chemical compounds for toxicity was developed. The test is based on direct measurement of the inhibition of microbial dehydrogenase activity, as affected by a toxicant, in a well buffered DMSO‐resazurin solution. The addition of 5% DMSO to the reaction mixture allows the toxicity determination of compounds with low water solubility, thus facilitating measurement of the effects of important environmental contaminants on microbiota. The test has been applied to 15 selected chemicals which represent a vast range of environmental contaminants. As well as a routine screening procedure for chemical toxicity, this new resazurin test can be used as a tool in the study of structure‐activity relationship.
Testing the antimicrobial activity of compounds from the air of animal houses using the microtox test
Authors: Hartung J.
Published: October 2006

A large number of different chemical compounds can be found in the air of densely populated animal production houses. These compounds may influence animal performance and health. Although knowledge of the biological activity of such compounds is limited in these situations, bioassays with animals are expensive, complicated to perform and evaluate. At the same time there is an increasing interest in simple and reliable test methods avoiding the use of laboratory animals. Microbial short‐term assays offer many advantages, particularly for screening purposes.

The recently introduced Microtox assay was used to test the toxicity of eight single air contaminants, 13 two‐compound mixtures, and some extracts from aerosols and dust from a confined pig fattening house. p‐Cresol was the most toxic with an EC50 (15 min) value of 0.015 mM followed by m‐cresol (0.074 mM), butyric acid (0.115 mM), dimethylamine (0.156 mM), formaldehyde (0.25 mM), phenol (0.46 mM), butanol (32 mM), and acetone (258 mM). The coefficients of variation for five replicates of these compounds ranged from about 5% (m‐cresol) to 24% (dimethylamine).

The two‐compound mixtures showed mainly synergistic or antagonistic effects. The investigation of the aerosol extracts showed that increasing aerosol amounts also increase the necessary dilution ratio to reach the EC50 (15 min) value. Futhermore, it was observed that the dust extract can stimulate the growth of Photobacterium phosphoreum (as determined by plate counts) although the bioluminescence is ceased. Apparently the inhibition of the light output of the bacteria is not necessarily accompanied by a loss of viability.
Comparison of cell‐free and whole cell luminescence assays in toxicity testing
Authors: Surowitz Kenneth G. , Burke Brian E. , Pfister Robert M.
Published: October 2006

The effects of eight organic and eight inorganic compounds on light emission by two cell‐free bioluminescent systems were compared to the effects of these substances on light emission by whole cells of Photobacterium phosphoreum (Microtox® strain). Crude luciferase preparations from the firefly (Photoniuspyralis) and Vibrio (Photobacterium) fischeri were exposed to the toxicants at or near the Microtox EC50 values for 0.25, 5, or 15 min and then reacted with the necessary reagents for luminescence (ATP for the firefly reaction; NADH, FMN and n‐decylaldehyde for the bacterial extract). The light emission values, relative to controls, were then compared to those obtained after exposure of P. phosphoreum cells to the toxicants for the same duration. The three systems were found to differ in both response time and sensitivity. The firefly extract was found to be most sensitive to inorganics while whole cells of P. phosphoreum were most sensitive to organics after 0.25 min of exposure. However, after 5 and 15 min both systems were nearly equivalent in their sensitivity to the test toxicants. The V. fishceri cell extract was found to be extremely sensitive to three of the inorganics tested at 0.25 minutes, but was either unaffected or stimulated by the remaining inorganic and organic compounds at all times examined. Our results indicate that the sensitivity of detection of certain toxic compounds may be optimized by selection of a particular luminescent system.
Genotoxicity studies on sediments using a modified SOS chromotest
Authors: Dutka B. J. , Kwan K. K.
Published: October 2006

Noting that the inducibility of samples tested with the SOS Chromotest increased with increasing colour development time, a slightly modified Chromotest procedure was developed and applied to six sediment samples from Prince Edward Island. The samples tested by this newly developed short‐term genotoxicity test showed weak inducibility expressed by the SOSIP—SOS Inducing Potency. Five of the six samples were activated by the addition of S‐9 fraction, commonly used with the Ames/Microsome test. Only one of the samples showed toxic activity by the Microtox test.
The SOS chromotest kit: A rapid method for the detection of genotoxicity
Authors: Fish F. , Lampert I. , Halachmi A. , Riesenfeld G. , Herzberg M.
Published: October 2006

The SOS Chromotest is a bacterial assay for genotoxicity, based on the detection of damage to DNA as measured through the SOS DNA repair system. An E. coli strain was derived by fusing the structural lacZ gene with a promoter of one of the SOS genes, namely the sfiA gene. Auxiliary mutations increase the sensitivity of the Chromotest bacteria to genotoxic materials. In the SOS Chromotest, any damage to the DNA results in the activation of the SOS system, including the sfiA gene promoter. This, in turn, induces the de novo transcription and synthesis of the enzyme B. galactosidase. The enzyme is clearly and easily detected by a chromogenic reaction. We have miniaturized the SOS Chromotest and developed it into a self‐contained kit in the microtitration format. The kit contains all the components of the test, including dried bacteria and a dried liver S‐9 mix in a stable state, allowing on‐site operation. The whole test, including the revival of the bacteria, can be completed in 6–7 hours. In addition to being used as a genotoxics detection and monitoring system in chemical, cosmetics, food and pharmaceutical industries, the advantages of the rapid SOS Chromotest can be exploited in full for environmental and occupational health studies. In order to circumvent tedious concentrations of samples (e.g., urine, water), we have tried to further increase the sensitivity of the Chromotest by exposing the bacteria to relatively large volumes of unconcentrated samples. Employing this approach, we were able to demonstrate genotoxic activity in unconcentrated urine samples obtained from people exposed to environmental genotoxins. It appears, therefore, that the SOS Chromotest kit will allow an economically feasible and efficient monitoring of genotoxics in the environment.
Evaluation of the formazan extraction step of Int‐dehydrogenase assay
Authors: Lee C.‐W. , Koopman B. , Bitton G.
Published: October 2006

An essential part of in vivo INT‐dehydrogenase assay is quantitation of the intensely colored, water‐insoluble iodonitrotetrazolium formazan (INTF) that forms intracellularly as the product of INT reduction. This procedure involves extraction of INTF from microbial cells by an organic solvent, permitting colorimetric measurement of the formazan. In the present study, it was found that dimethylsulfoxide (DMSO) provided the most consistent extraction of INTF from activated sludge and filamentous bacteria. The relative efficiency of 2 + 3 tetrachloroethylene/acetone (TA) was slightly greater than that of DMSO in some cases. However, this solvent only partially extracted INTF from one of the filament types tested (type 1701) and its performance was impaired by adsorption of ferrous ion to sludge. Methanol was generally the least efficient of the solvents tested. It was particularly ineffective in extracting INTF from Fe2+‐treated sludges. Permeabilization of cells with lysozyme or Triton X‐100 improved the INTF yields obtained with methanol. Triton X‐100,the more effective of the two permeabilizing agents, increased the INTF yield obtained with methanol to the same level as that obtained with DMSO or TA.
Induction of SOS function in Escherichia coli by some mycotoxins
Authors: Auffray Y. , Boutibonnes P.
Published: October 2006

The genotoxic activity of 11 mycotoxins was investigated in Escherichia coli K12. The induction of the SOS function s fi A whose level of expression is monitored by means of a s fi A :: lac Z operon fusion was assayed by measuring the β‐galactosidase activity in the PQ 37 strain. Most of these fungal metabolites did not induce SOS response in this bacterial test. Only aflatoxicol, a reduced metabolite of aflatoxin B1, was well detected as an SOS inducer if metabolic activation was performed. Patulin, penicillic acid, and viomellein were only weak inducing agents. The other fungal compounds tested failed to demonstrate a positive SOS inducing activity. The relationship between the SOS Chromotest, mutagenicity to Salmonella typhimurium, and in vivo carcinogenicity was discussed.
Naturally occurring fecal coliforms and fecal streptococci in Hawaii's freshwater streams
Authors: Fujioka Roger S. , Tenno Kenneth , Kansako Sidney
Published: October 2006

The recreational quality of stream water in Hawaii was assessed by carefully analyzing stream, sewage, cesspool, and storm drain samples for concentrations of fecal coliform (FC), fecal streptococcus (FS), and selected physical and chemical parameters. High concentrations of FC, far in excess of the recreational water quality standard of 200 FC/100 mL, could be readily recovered from streams with no obvious sources of pollution and increased dramatically as the stream flowed through urbanized areas. Since sewage and cesspool wastes were characterized by a high (>4) FC: FS ratio, whereas stream water and storm drain samples had a low (<0.7) FC: FS ratio, it was concluded that the source of indicator bacteria in streams was not sewage or cesspool but most likely land runoff. The concentrations of indicator bacteria in treated sewage effluent being discharged into streams were determined to be much lower than the concentrations present in the receiving stream water. Thus, the impact of sewage effluent discharge into the streams of Hawaii cannot be properly evaluated by analyzing stream water samples for FC as mandated by law. Concentrations of orthophosphate, which is low in streams and high in sewage, was determined to be a reliable indicator for the presence of sewage effluent in streams.
Cervical length in women in preterm labor with intact membranes: relationship to intra‐amniotic inflammation/microbial invasion, cervical inflammation and preterm delivery
Authors: Holst R.‐M. , Jacobsson B. , Hagberg H. , Wennerholm U.‐B.
Published: October 2006

Objective

Intra‐amniotic infection, diagnosed by microbial invasion of the amniotic cavity (MIAC) and/or the presence of intra‐amniotic inflammation (IAI), is related to adverse perinatal outcome in women with preterm labor. Due to the subclinical nature of IAI, a correct diagnosis depends on amniocentesis, which is an invasive method not performed as a clinical routine. The aim of this study was to evaluate if cervical length measured by transvaginal sonography could assist in the identification of women at high risk for IAI.

Methods

Cervical length was assessed by transvaginal sonography in 87 women with singleton pregnancies in preterm labor (< 34 weeks of gestation). Cervical (n = 87) and amniotic (n = 55) fluids were collected. Polymerase chain reactions for Ureaplasma urealyticum and Mycoplasma hominis, and culture for aerobic and anaerobic bacteria, were performed. Interleukin (IL)‐6 and IL‐8 were analyzed by enzyme‐linked immunosorbent assay.

Results

IAI was present in 25/55 (45%) of the patients presenting with preterm labor who underwent amniocentesis. Women with IAI had a significantly shorter cervical length (median, 10 (range, 0–34) mm) than had those without IAI (median, 21 (range, 11–43) mm) (P < 0.0001). Receiver–operating characteristics curve analysis showed that a cervical length (cut‐off of 15 mm) predicted IAI (relative risk, 3.6; CI, 1.9–10.0) with a sensitivity of 72%, specificity of 83%, positive predictive value of 78% and negative predictive value of 78%. Cervical length was also significantly associated with preterm birth up to 7 days from sampling and at ≤ 34 weeks.

Conclusion

Cervical length assessed by transvaginal sonography predicts IAI as well as preterm birth and could thereby be a useful clinical tool in the management of patients in preterm labor. Copyright © 2006 ISUOG. Published by John Wiley & Sons, Ltd.
Diazoxide acts more as a PKC‐ɛ activator, and indirectly activates the mitochondrial KATP channel conferring cardioprotection against hypoxic injury
Authors: Kim M‐Y , Kim M J , Yoon I S , Ahn J H , Lee S H , Baik E J , Moon C‐H , Jung Y‐S
Published: October 2006

Background and purpose:

Diazoxide, a well‐known opener of the mitochondrial ATP‐sensitive potassium (mitoKATP) channel, has been demonstrated to exert cardioprotective effect against ischemic injury through the mitoKATP channel and protein kinase C (PKC). We aimed to clarify the role of PKC isoforms and the relationship between the PKC isoforms and the mitoKATP channel in diazoxide‐induced cardioprotection.

Experimental approach:

In H9c2 cells and neonatal rat cardiomyocytes, PKC‐ɛ activation was examined by Western blotting and kinase assay. Flavoprotein fluorescence, mitochondrial Ca2+ and mitochondrial membrane potential were measured by confocal microscopy. Cell death was determined by TUNEL assay.

Key results:

Diazoxide (100 μM) induced translocation of PKC‐ɛ from the cytosolic to the mitochondrial fraction. Specific blockade of PKC‐ɛ by either ɛV1‐2 or dominant negative mutant PKC‐ɛ (PKC‐ɛ KR) abolished the anti‐apoptotic effect of diazoxide. Diazoxide‐induced flavoprotein oxidation was inhibited by either ɛV1‐2 or PKC‐ɛ KR transfection. Treatment with 5‐hydroxydecanoate (5‐HD) did not affect translocation and activation of PKC‐ɛ induced by diazoxide. Transfection with wild type PKC‐ɛ mimicked the flavoprotein‐oxidizing effect of diazoxide, and this effect was completely blocked by ɛV1‐2 or 5‐HD. Diazoxide prevented the increase in mitochondrial Ca2+, mitochondrial depolarization and cytochrome c release induced by hypoxia and all these effects of diazoxide were blocked by ɛV1‐2 or 5‐HD.

Conclusions and Implications:

Diazoxide induced isoform‐specific translocation of PKC‐ɛ as an upstream signaling molecule for the mitoKATP channel, rendering cardiomyocytes resistant to hypoxic injury through inhibition of the mitochondrial death pathway.

British Journal of Pharmacology (2006) 149, 1059–1070. doi:10.1038/sj.bjp.0706922
In vivo evidence that 5‐HT2C receptors inhibit 5‐HT neuronal activity via a GABAergic mechanism
Authors: Boothman L , Raley J , Denk F , Hirani E , Sharp T
Published: October 2006

Background and purpose:

Recent evidence suggests that 5‐HT2C receptor activation may inhibit midbrain 5‐HT neurones by activating neighbouring GABA neurones. This hypothesis was tested using the putative selective 5‐HT2C receptor agonist, WAY 161503.

Experimental approach:

The effect of WAY 161503 on 5‐HT cell firing in the dorsal raphe nucleus (DRN) was investigated in anaesthetised rats using single unit extracellular recordings. The effect of WAY 161503 on DRN GABA neurones was investigated using double label immunohistochemical measurements of Fos, glutamate decarboxylase (GAD) and 5‐HT2C receptors. Finally, drug occupancy at 5‐HT2A receptors was investigated using rat positron emission tomography and ex vivo binding studies with the 5‐HT2A receptor radioligand [11C]MDL 100907.

Key results:

WAY 161503 caused a dose‐related inhibition of 5‐HT cell firing which was reversed by the 5‐HT2 receptor antagonist ritanserin and the 5‐HT2C receptor antagonist SB 242084 but not by the 5‐HT1A receptor antagonist WAY 100635. SB 242084 pretreatment also prevented the response to WAY 161503. The blocking effects of SB 242084 likely involved 5‐HT2C receptors because the drug did not demonstrate 5‐HT2A receptor occupancy in vivo or ex vivo. The inhibition of 5‐HT cell firing induced by WAY 161503 was partially reversed by the GABAA receptor antagonist picrotoxin. Also, WAY 161503 increased Fos expression in GAD positive DRN neurones and DRN GAD positive neurones expressed 5‐HT2C receptor immunoreactivity.

Conclusions and implications:

These findings indicate that WAY 161503 inhibits 5‐HT cell firing in the DRN in vivo, and support a mechanism involving 5‐HT2C receptor‐mediated activation of DRN GABA neurones.

British Journal of Pharmacology (2006) 149, 861–869. doi:10.1038/sj.bjp.0706935
Study of room temperature magnetoelectric coupling in Ti substituted bismuth ferrite system
Authors: Kumar Manoj , Yadav K. L.
Published: October 2006

Dielectric, magnetic, and magnetoelectric properties of Ti substituted bismuth ferrite (BiFeO3) ceramic synthesized by solid state reaction are reported. Ti substitution for Fe in BiFeO3 increased the room temperature electrical resistivity by approximately six orders of magnitude and also increased the dielectric constant and reduced the loss tangent. The remanent polarization, coercive field, and maximum polarization were 0.081μC∕cm2, 2.571kV∕cm, and 0.658μC∕cm2, respectively at 20kV∕cm. An anomaly in the dielectric constant and loss tangent around Néel temperature was observed. The ferroelectric and magnetic hysteresis loops were measured which are not really saturated in BiFe0.75Ti0.25O3 compound and represented a partial reversal. The magnetoelectric coupling between electric dipoles and magnetic dipoles at room temperature was demonstrated by measuring the effect of magnetic poling on ferroelectric hysteresis loop and the change in the dielectric constant with the external magnetic field.
Comparative studies of molecular reorientations in thermal-assisted and photoassisted electric-field poled nonlinear optical polymers
Authors: To C. W. , Wong K. Y.
Published: October 2006

The reorientational mobilities of molecules in nonlinear optical (NLO) polymers poled by thermal-assisted (TAP) and photoassisted (PAP) electric-field polings are compared by measuring the temporal development of the NLO properties under a secondary poling voltage at a temperature below the glass transition temperature of the polymer. By comparing the experimental results with a theoretical model that is based on a distribution of relaxation times, it was found that the experimental poling profile for a polymer poled by PAP showed a good agreement with the theory, while that for a polymer poled by TAP did not. The discrepancy of the behaviors between the two poling methods suggests that the relaxation patterns observed for polymers poled by TAP may not behave in a manner intrinsic to the polymer.
In situ monitoring of the growth of ice films by laser picosecond acoustics
Authors: Kashiwada Saori , Matsuda Osamu , Baumberg Jeremy J. , Li Voti Roberto , Wright Oliver B.
Published: October 2006

Ultrashort optical pulses are used to excite and probe picosecond acoustic pulses in a sample consisting of an opaque material upon which ice is continuously deposited from the vapor phase at ∼110K. By analysis of the ultrasonic propagation and reflection inside the submicron ice film and taking into account the scattering of the probe light by the acoustic waves, the thickness, sound velocity, refractive index, ultrasonic attenuation, and photoelastic constant of the ice film are derived. This method should find applications for the in situ monitoring of thin transparent films during growth.
Work function analysis of GaN-based lateral polarity structures by Auger electron energy measurements
Authors: Niebelschütz M. , Ecke G. , Cimalla V. , Tonisch K. , Ambacher O.
Published: October 2006

Lateral polarity heterostructure (LPH) was grown with adjacent Ga- and N-face domains in order to invert the polarity of the crystal within a periodicity of a few microns. In this study we focus on the analysis of these LPH by Auger electron spectroscopy (AES). Because of the relationship between the Auger electron energy and the Fermi level, AES is a suitable method to identify the domains of a lateral polarity heterostructure. In addition, we discuss the possibility of determining the work function difference of Ga- and N-face GaN. This difference in the work function between Ga-face and N-face GaN is found to be 0.25eV. This difference is caused by a surface band bending.
Electronic structure of C60 on Au(887)
Authors: Schiller F. , Ruiz-Osés M. , Ortega J. E. , Segovia P. , Martínez-Blanco J. , Doyle B. P. , Pérez-Dieste V. , Lobo J. , Néel N. , Berndt R. , Kröger J.
Published: October 2006

We present an analysis of the electronic structure of C60 adsorbed on a vicinal Au(111) surface at different fullerene coverages using photoemission, x-ray absorption, and scanning tunneling microcopy/spectroscopy (STS). STS provides a straightforward determination of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) levels with respect to the Fermi energy. At C60 coverages of 0.5 and 1 ML a 2.7eV wide HOMO-LUMO gap is found. The near-edge x-ray absorption fine structure (NEXAFS) spectrum for the 0.5 ML C60 nanomesh structure displays a significant intensity at the low energy side of the LUMO exciton peak, which is explained as due to absorption into HOMO-LUMO gap states localized at individual C60 cluster edges. From 0.5 to 1 ML we observe a rigid shift of the HOMO-LUMO peaks in the STS spectra and an almost complete quenching of the gap states feature in NEXAFS.
Solid-liquid nuclear magnetic resonance relaxation and signal amplitude relationships with ranking of seasoned softwoods and hardwoods
Authors: Fantazzini P. , Maccotta A. , Gombia M. , Garavaglia C. , Brown R. J. S. , Brai M.
Published: October 2006

In H1 NMR (nuclear magnetic resonance) relaxation measurements for a set of eight hardwood and softwood samples, each free induction decay (FID) is fitted by the sum of a “solid” signal of the form Aexp[−c(t∕TS)2][1−g(t∕TS)2+h(t∕TS)4] plus a “liquid” signal Bexp(−t∕T2-FID). Distributions of longitudinal (T1) relaxation times were computed separately for the solid and liquid components, giving also the solid/liquid H1 ratio α. From measurements on the samples dried, seasoned, and hydrated, the moisture content (liquid/solid weight ratio) was found to be approximately 0.50∕α. For each of the “seasoned” samples (10%–13% moisture content) a single T1 peak was found for the solid and two for the liquid, with the longer liquid T1 close to that of the solid, but with some differences exceeding perceived experimental uncertainties. None of the solid or liquid-long T1’s is much less than 20ms, even though liquid-short times go as low as 0.35ms, appearing to negate simple solid-to-liquid exchange on a millisecond time scale. Data for six of the samples (all except for two resin-containing pine species) can be formally fitted by a two-site exchange model, in which cases the solid-to-liquid exchange times are a few tens of milliseconds. For our set of wood samples, each of the above three T1 values, and also the overall liquid geometric-mean and rate-average T1’s, as well as the liquid long-T1 fraction, for a seasoned hardwood is longer than the corresponding value for any softwood, suggesting that relaxation parameters may provide a useful ranking of seasoned woods.
Surface-enhanced Raman scattering from Ag nanoparticles formed by visible laser irradiation of thermally annealed AgOx thin films
Authors: Fujimaki Makoto , Awazu Koichi , Tominaga Junji , Iwanabe Yasuhiko
Published: October 2006

Visible laser irradiation of AgOx thin films forms Ag nanoparticles, which then results in surface-enhanced Raman scattering (SERS). The efficiency of this Ag nanoparticle formation strongly depends on the properties of the AgOx thin films. Thermal annealing causes changes in physical properties such as deoxidization of the films and aggregation of Ag atoms in the films. In the present research, the effects of the changes induced by thermal annealing on SERS efficiency were examined. It was found that AgOx thin films annealed at 300°C for 5min in a N2 atmosphere were suitable for the formation of Ag nanoparticles effective for SERS, while films that were not annealed were not. From these results, it was deduced that the Ag aggregation resulting from thermal annealing in AgOx thin films promotes the Ag nanoparticle formation.
Spinodal induced homogeneous nanostructures in magnetoresistive CoCu granular thin films
Authors: Mebed A. M. , Howe J. M.
Published: October 2006

A process for producing a dispersion of nanometer-sized, Co-rich particles embedded in a thin film of Cu-rich matrix is presented. Thin films were prepared by thermal evaporation of a bulk CoCu alloys on an amorphous C substrate. In situ transmission electron microscopy (TEM) and field-emission gun TEM equipped with an energy dispersive x-ray spectrometer were used to investigate spinodal decomposition of the initial homogeneous thin film alloy. The maximum giant magnetoresistance (GMR) is found to be 18% for a Co45Cu55 after heating the film from room temperature at 2°C∕minto204°C and holding for 10min. These nanostructures are expected to exhibit optimum GMR for granules having higher Co content.
Coupled-cluster studies of the electronic excitation spectra of silanes
Authors: Lehtonen Olli , Sundholm Dage
Published: October 2006

The electronic excitation spectra of unsubstituted linear silanes (n-SimH2m+2, m=1-6), cyclopentasilane (c-Si5H10), and neopentasilane (neo-Si5H12) have been studied at the coupled-cluster approximate singles and doubles (CC2) level using Dunning’s quadruple-ζ basis sets augmented with diffuse functions (aug-cc-pVQZ). Comparisons with measured ultraviolet spectra for Si2H6 and n-Si3H8 show that CC2 calculations using these basis sets yield excitation energies in good agreement with experiment. The calculated excitation thresholds for Si2H6 and n-Si3H8 of 7.61 and 6.68eV are only 0.05eV larger than the gas-phase values of 7.56 and 6.63eV, respectively. For n-Si4H10, n-Si5H12, and neo-Si5H12, the calculated excitation thresholds of 6.51, 6.14, and 6.87eV for the lowest dipole-allowed transitions are about 0.4eV larger than the corresponding liquid-phase data of 6.05, 5.77, and 6.53eV; the discrepancy can mainly be attributed to solvent effects. The obtained excitation thresholds for n-Si6H14 is 5.85eV, whereas no experimental data are available for its optical gap. Calculations using the Karlsruhe triple-ζ valence basis sets augmented with single and double sets of polarization functions show that very large basis sets augmented with diffuse functions are needed for obtaining accurate excitation energies. The optical gaps for silanes obtained using the triple-ζ polarization basis sets were found to be 0.4 and 0.2eV larger than those obtained using Dunning’s quadruple-ζ basis sets. Excitation thresholds calculated at density functional theory levels using generalized gradient approximation are 0.7–1.0eV smaller than the experimental values and by employing hybrid functionals they are 0.3–0.4eV below the experimental thresholds. By adding the present basis-set correction and environmental effects to the previously calculated CC2 value for the excitation threshold of the Si29H36 silicon nanocluster, the extrapolated absorption threshold is 4.0eV as compared to the recently reported experimental value of 3.7eV.
The giant magnetocaloric effect of Gd5Si1.95Ge2.05 enhanced by Sn doping
Authors: Li J. Q. , Sun W. A. , Jian Y. X. , Zhuang Y. H. , Huang W. D. , Liang J. K.
Published: October 2006

The effects of tin substitution on the phase formation, the Curie temperature, and the magnetic entropy change of the monoclinic Gd5Si1.95Ge2.05 alloy have been investigated. Five Sn-doped Gd5Si1.95−xGe2.05−xSn2x samples were prepared with 2x=0, 0.01, 0.03, 0.05, and 0.10, respectively. Experimental results show that a small amount of Sn doping in Gd5Si1.95Ge2.05 retains the first order structural/magnetic transition, significantly enhances its magnetocaloric effects as well as increase its Curie temperature Tc, but leads to increase in hysteresis loss due to its field-induced monoclinic to orthorhombic phase transformation. The maximum magnetic entropy change of the Sn-doped Gd5Si1.935Ge2.035Sn0.03 sample for the 0–2.0T magnetic field change reaches 28.9Jkg−1K−1 at 277K, which is twice as large as that of pure Gd5Si1.95Ge2.05 (14.1Jkg−1K−1 at 260K) for the same magnetic field change.
Dynamic-force spectroscopy measurement with precise force control using atomic-force microscopy probe
Authors: Takeuchi Osamu , Miyakoshi Takaaki , Taninaka Atsushi , Tanaka Katsunori , Cho Daichi , Fujita Machiko , Yasuda Satoshi , Jarvis Suzanne P. , Shigekawa Hidemi
Published: October 2006

The accuracy of dynamic-force spectroscopy (DFS), a promising technique of analyzing the energy landscape of noncovalent molecular bonds, was reconsidered in order to justify the use of an atomic-force microscopy (AFM) cantilever as a DFS force probe. The advantages and disadvantages caused, for example, by the force-probe hardness were clarified, revealing the pivotal role of the molecular linkage between the force probe and the molecular bonds. It was shown that the feedback control of the loading rate of tensile force enables us a precise DFS measurement using an AFM cantilever as the force probe.
Effect of chirality on buckling behavior of single-walled carbon nanotubes
Authors: Zhang Y. Y. , Tan V. B. C. , Wang C. M.
Published: October 2006

In this paper, molecular dynamics simulations (MDS) are performed on single-walled carbon nanotubes (SWCNTs) in order to study the effects of chirality on their buckling behavior under axial compression. In the MDS, the Tersoff-Brenner potential is used to describe the interaction of carbon atoms in the SWCNTs. The sensitivity of the buckling strains and buckling modes with respect to the chirality of SWCNT is investigated by modeling SWCNTs with different chiral angles, varying from 0° to 30°, but keeping the length-to-diameter ratio constant. The carbon nanotubes are also analyzed using a continuum cylindrical shell model based on the theory of nonlocal elasticity so as to assess its validity in predicting the buckling strains when compared with the results that are obtained by MDS. The differences between the buckling strains at the continuum scale and that at the nanoscale are also studied. The present analysis and results are helpful in understanding the buckling behaviors of axially compressed carbon nanotubes. This knowledge is important for the application of carbon nanotubes as building blocks of nanomechanical devices.
Magnetization reversal of FePt hard/soft stacked nanocomposite particle assembly
Authors: Takahashi Y. K. , Hono K. , Okamoto S. , Kitakami O.
Published: October 2006

Microstructure and magnetic properties of interfacially disordered FePt nanoparticles with a diameter of about 10nm were investigated. Sputter deposition of amorphous Al2O3 overlayer caused the disordering of L10-FePt particles at the interface. The assembly of these partially disordered FePt nanoparticles is equivalent to the composite medium consisting of the exchange coupled soft and hard layers. Coercivity Hc of the interfacially disordered FePt nanoparticles significantly decreased with increasing thickness of the disordered layer. Comparison with theoretical calculations has shown that this reduction of Hc is attributed to the so-called spin flop state during the magnetization reversal. The interfacial disordering method has been demonstrated to be a promising technique for fabricating FePt-based soft/hard stacked composite media.
Influence of impact parameters of zirconia droplets on splat formation and morphology in plasma spraying
Authors: Shinoda Kentaro , Koseki Toshihiko , Yoshida Toyonobu
Published: October 2006

In this study, the effects of the impact parameters, namely, the diameter d0, velocity V0, and temperature T0, of an impacting droplet of yttria-stabilized zirconia (YSZ) on splat morphology have been investigated systematically under plasma spraying conditions. In particular, fully molten droplets of 30–90μm in d0 that impact on a preheated quartz glass substrate at V0 of 10–70m∕s have been examined via hybrid plasma spraying. The degree of flattening of final splat morphology, ξ, was found to be predicted by the relationship ξ=0.43Re1∕3, where Re is the Reynolds number. The dimensionless spreading time of droplets, ts*=tsV0∕d0, was distributed around 2.7, where ts is the spreading time of the droplet. The ideal maximum spread factor derived from the splat height was approximately proportional to Re1∕4. The latter two findings suggest that the analytical model developed by Pasandideh-Fard et al. [Phys. Fluids 8, 650 (1996)] can be applied to the droplet impact in plasma spraying especially for the case of YSZ. In addition, the thermal contact resistance of disk shaped splats decreased with the increase of V0 within the range of 10−5–10−6m2K∕W.
Internal electric fields of electrolytic solutions induced by space-charge polarization
Authors: Sawada Atsushi
Published: October 2006

The dielectric dispersion of electrolytic solutions prepared using chlorobenzene as a solvent and tetrabutylammonium tetraphenylborate as a solute is analyzed in terms of space-charge polarization in order to derive the ionic constants, and the Stokes radius obtained is discussed in comparison with the values that have been measured by conductometry. A homogeneous internal electric field is assumed for simplicity in the analysis of the space-charge polarization. The justification of the approximation by the homogeneous field is discussed from two points of view: one is the accuracy of the Stokes radius value observed and the other is the effect of bound charges on electrodes in which they level the highly inhomogeneous field, which has been believed in the past. In order to investigate the actual electric field, numerical calculations based on the Poisson equation are carried out by considering the influence of the bound charges. The variation of the number of bound charges with time is clarified by determining the relaxation function of the dielectric constant attributed to the space-charge polarization. Finally, a technique based on a two-field approximation, where homogeneous and hyperbolic fields are independently applied in relevant frequency ranges, is introduced to analyze the space-charge polarization of the electrolytic solutions, and further improvement of the accuracy in the determination of the Stokes radius is achieved.
Gaseous scintillation detection and amplification in variable pressure scanning electron microscopy
Authors: Morgan S. W. , Phillips M. R.
Published: October 2006

This work investigates the generation and detection of gaseous scintillation signals produced in variable pressure scanning electron microscopy through electron-gas molecule excitation reactions. Here a gaseous scintillation detection (GSD) system is developed to efficiently detect photons produced via excitation reactions in electron cascades. Images acquired using GSD are compared to those obtained using conventional gaseous secondary electron detection (GSED) and demonstrate that images rich in secondary electron (SE) contrast can be achieved using the gaseous scintillation signal. A theoretical model, based on existing Townsend theories, is developed. It describes the production and amplification of photon signals generated by cascading SEs, high energy backscattered electrons, and primary beam electrons. Photon amplification (the total number of photons produced per sample emissive electron) is then investigated and compared to conventional electronic amplification over a wide range of microscope operating parameters, scintillating imaging gases, and photon collection geometries. These studies revealed that argon gas exhibited the largest GSD gain, followed by nitrogen then water vapor, exactly opposite to the trend observed for electron amplification data. It was also found that detected scintillation signals exhibit larger SE signal-to-background levels compared to those of conventional electronic signals detected via GSED. Finally, dragging the electron cascade towards the light pipe assemblage of GSD systems, or electrostatic focusing, dramatically increases the collection efficiency of photons.
Formation of silicon nanocrystals in sapphire by ion implantation and the origin of visible photoluminescence
Authors: Yerci S. , Serincan U. , Dogan I. , Tokay S. , Genisel M. , Aydinli A. , Turan R.
Published: October 2006

Silicon nanocrystals, average sizes ranging between 3 and 7nm, were formed in sapphire matrix by ion implantation and subsequent annealing. Evolution of the nanocrystals was detected by Raman spectroscopy and x-ray diffraction (XRD). Raman spectra display that clusters in the matrix start to form nanocrystalline structures at annealing temperatures as low as 800°C in samples with high dose Si implantation. The onset temperature of crystallization increases with decreasing dose. Raman spectroscopy and XRD reveal gradual transformation of Si clusters into crystalline form. Visible photoluminescence band appears following implantation and its intensity increases with subsequent annealing process. While the center of the peak does not shift, the intensity of the peak decreases with increasing dose. The origin of the observed photoluminescence is discussed in terms of radiation induced defects in the sapphire matrix.
On the modulation mechanisms in photoreflectance of an ensemble of self-assembled InAs∕GaAs quantum dots
Authors: Motyka M. , Sęk G. , Kudrawiec R. , Misiewicz J. , Li L. H. , Fiore A.
Published: October 2006

We present the investigation of the modulation mechanisms in photoreflectance (PR) spectroscopy of an ensemble of self-assembled semiconductor quantum dots (QDs). In order to distinguish between possible factors contributing to the total modulation efficiency of QD transitions, a photoreflectance excitation experiment has been performed on an InAs∕GaAs quantum dot structure grown by solid-source molecular beam epitaxy. It has been observed that the intensity of PR features related to QDs changes in a function of the wavelength of the pumping laser, tuned from above-GaAs band gap down to below wetting layer ground state transition. Based on this dependence we have shown that most of the QD PR signal intensity originates from the modulation of the built-in electric field caused by carriers photogenerated in GaAs layers. We also conclude that the modulation of QD transitions related to a possible modification of the dot properties due to filling them with carriers is negligible in PR experiment on an ensemble of dots. An additional confirmation of the PR results has been obtained by using contactless electroreflectance (CER), demonstrating that the line shape of PR and CER QD resonances is almost identical in both spectra. Thus, the QD transitions can be analyzed by using the standard low field line shape functional form applicable in any electromodulation spectroscopy.
Nature of reactive O2 and slow CO2 evolution kinetics in CO oxidation by TiO2 supported Au cluster
Authors: Pala Raj Ganesh S. , Liu Feng
Published: October 2006

Recent experiments on CO oxidation reaction using seven-atom Au clusters deposited on TiO2 surface correlate CO2 formation with oxygen associated with Au clusters. We perform first principles calculations using a seven-atom Au cluster supported on a reduced TiO2 surface to explore potential candidates for the form of reactive oxygen. These calculations suggest a thermodynamically favorable path for O2 diffusion along the surface Ti row, resulting in its dissociated state bound to Au cluster and TiO2 surface. CO can approach along the same path and react with the O2 so dissociated to form CO2. The origin of the slow kinetic evolution of products observed in experiments is also investigated and is attributed to the strong binding of CO2 simultaneously to the Au cluster and the surface.
Kinetic simulation of an extreme ultraviolet radiation driven plasma near a multilayer mirror
Authors: van der Velden M. H. L. , Brok W. J. M. , van der Mullen J. J. A. M. , Banine V.
Published: October 2006

Future generation lithography tools will use extreme ultraviolet radiation to enable the printing of sub-50 nanometer features on silicon wafers. The extreme ultraviolet radiation, coming from a pulsed discharge, photoionizes the low pressure background gas in the tool. A weakly ionized plasma is formed, which will be in contact with the optical components of the lithography device. In the plasma sheath region ions will be accelerated towards the surfaces of multilayer mirrors. A self-consistent kinetic particle-in-cell model has been applied to describe a radiation driven plasma. The simulations predict the plasma parameters and notably the energy at which ions impact on the plasma boundaries. We have studied the influence of photoelectron emission from the mirror on the sheath dynamics and on the ion impact energy. Furthermore, the ion impact energy distribution has been convoluted with the formula of Yamamura and Tawara [At. Data Nucl. Data Tables 62, 149 (1996)] for the sputter yield to obtain the rate of physical sputtering. The model predicts that the sputter rate is dominated by the presence of doubly ionized argon ions.
Efficient energy transfer from Si clusters to Er3+ in complex silicate glasses
Authors: Lebour Y. , Pellegrino P. , García C. , Moreno J. A. , Garrido B.
Published: October 2006

We present an extensive study of the structural and optical emission properties in aluminum silicates and soda-lime silicates codoped with Si nanoclusters (Si-nc) and Er. Si excess of 5 and 15at.% and Er concentrations ranging from 2×1019 up to 6×1020cm−3 were introduced by ion implantation. Thermal treatments at different temperatures were carried out before and after Er implantation. Structural characterization of the resulting structures was performed to obtain the layer composition and the size distribution of Si clusters. A comprehensive study has been carried out of the light emission as a function of the matrix characteristics, Si and Er contents, excitation wavelength, and power. Er emission at 1540nm has been detected in all coimplanted glasses, with similar intensities. We estimated lifetimes ranging from 2.5to12ms (depending on the Er dose and Si excess) and an effective excitation cross section of about 1×10−17cm2 at low fluxes that decreases at high pump power. By quantifying the amount of Er ions excited through Si-nc we find a fraction of 10% of the total Er concentration. Upconversion coefficients of about 3×10−18cm−3s−1 have been found for soda-lime glasses and one order of magnitude lower in aluminum silicates.
Effect of experimentally observed hydrogenic fractionation on inertial confinement fusion ignition target performance
Authors: McKenty P. W. , Wittman M. D. , Harding D. R.
Published: October 2006

The need of cryogenic hydrogenic fuels in inertial confinement fusion (ICF) ignition targets has been long been established. Efficient implosion of such targets has mandated keeping the adiabat of the main fuel layer at low levels to ensure drive energies are kept at reasonable minima. The use of cryogenic fuels helps meet this requirement and has therefore become the standard in most ICF ignition designs. To date most theoretical ICF ignition target designs have assumed a homogeneous layer of deuterium-tritium (DT) fuel kept slightly below the triple point. However, recent work has indicated that, as cryogenic fuel layers are formed inside an ICF capsule, isotopic dissociation of the tritium (T), deuterium (D), and DT takes place leading to a “fractionation” of the final ice layer. This paper will numerically investigate the effects that various scenarios of fractionation have on hot-spot formation, ignition, and burn in ICF ignition target designs.