bluuebunny/crossref_metadata_2025 huggingface dataset:
Photocurrent studies of stress and aging in pentacene thin film transistors
Authors: Fraboni Beatrice , Matteucci Andrea , Cavallini Anna , Orgiu Emanuele , Bonfiglio Annalisa
Published: November 2006

In this work the authors report on photocurrent spectroscopy analyses on pentacene thin film transistors that have been bias stressed and exposed to atmosphere over a long period of time (up to 80days). They have studied the charge transport properties and the electronic excited state energy and distribution of these organic thin film devices. They also have identified the major excitonic and band gap transition energies and have investigated their quite different behavior following exposure to atmosphere or to bias stress. Different charge carrier distributions and trapping phenomena are proposed to describe the observed effects.
Phase transition in Sr0.75Ba0.25NbO3 near the Curie temperature
Authors: Qadri Syed B. , Bellotti Jeffrey A. , Garzarella Anthony , Wieting Terence , Wu Dong Ho , Mahadik Nadeemullah A.
Published: November 2006

Strontium barium niobate has the tungsten-bronze structure with a tetragonal unit cell, and it exhibits negative thermal expansion along the c axis between −120°C and room temperature while having a positive thermal expansion along the a axis for the same temperature range. At higher temperatures, close to the Curie temperature and above, the negative thermal expansion along the c axis changes to positive thermal expansion. The a axis lattice parameter as a function of temperature shows a change in slope at the Curie temperature. These results indicate the presence of a second-order phase transition near the Curie temperature.
In situ magnetic field alignment of directly ordered L1 FePt nanoparticles
Authors: Qiu Jiao-Ming , Bai Jianmin , Wang Jian-Ping
Published: November 2006

Gas-phase prepared directly ordered FePt nanoparticles were shown to align with in situ magnetic fields. As shown by magnetic and x-ray diffraction data, a 3800Oe perpendicular field switched L10 FePt particles with a mean size of 6nm from in-plane arrangement in as-deposited state to out-of-plane orientation. A 5000Oe in-plane field successfully defined nanoparticles with in-plane texture. These results demonstrated the feasibility of preparing nanoparticle-based magnetic recording media and exchange-spring-type permanent magnets with desired magnetic orientation control. Only involving thermal fluctuation as the obstacle, this approach makes an ideal subject for theoretical understanding and further optimization.
Effect of electric field on exfoliation of nanoplates
Authors: Lu Wei , Koerner Hilmar , Vaia Richard
Published: November 2006

Nanocomposite performance relies on reproducible dispersion and arrangement of nanoparticles, such that the dominant morphology across macroscopic dimensions is nanoscopic. The impact of electric fields on the interaction of nanoplates is discussed for improving dispersion. For ideal dielectrics, an electric field may assist (or retard) exfoliation depending on the angle between a collection of plates and the field. A critical electric field strength for exfoliation is predicted. Structural refinement occurs by cleavage through the center of the stack. For lossy dielectrics, frequency can be tuned to cause exfoliation in all plate orientations.
Observation of femtosecond-laser-induced ablation plumes of aluminum using space- and time-resolved soft x-ray absorption spectroscopy
Authors: Okano Yasuaki , Oguri Katsuya , Nishikawa Tadashi , Nakano Hidetoshi
Published: November 2006

The dynamics of the laser ablation plume expansion of aluminum was investigated by using space- and time-resolved soft x-ray absorption spectroscopy. Blueshifts of the Al L-shell photoabsorption edge indicating the state of aluminum were observed in the plumes, which were generated by irradiating an aluminum target with 120fs near-infrared pulses at an intensity of 1014W∕cm2. The spatiotemporal evolution of the plumes exhibited a multilayer structure consisting of vaporized aluminum and condensed aluminum particles, following the expansion of plasma, with expansion velocities of 104m∕s for the atomic state and 103m∕s for the condensed state.
White-light-emitting phosphor: CaMgSi2O6:Eu2+, Mn2+ and its related properties with blending
Authors: Lee Sung Hun , Park Je Hong , Son Se Mo , Kim Jong Su , Park Hong Lee
Published: November 2006

The CaMgSi2O6:Eu2+, Mn2+ phosphors show three emission bands peaking at around 450nm (blue), 580nm (yellow), and 680nm (red). The blue band originates from the allowed f-d transition of Eu2+ ions on Ca sites. The yellow and red bands originate from the forbidden T14-A16 transition of Mn2+ ions on Mg2+ and Ca2+ sites, respectively. Electron paramagnetic resonance measurement demonstrates that Mn2+ ions occupy two different Ca2+ and Mg2+ sites. The mixtures of the green-poor CaMgSi2O6:Eu2+, Mn2+ and the green-to-yellow emissive (Ba,Sr)2SiO4:Eu2+, excited by the near ultraviolet of 365nm, show the various chromaticity of white light depending on the mixture ratio; the correlated color temperatures from 4845to9180K, and the color rendering indices from 71% to 88%.
Local electronic structure and luminescence properties of Er doped ZnO nanowires
Authors: Wang Juan , Zhou M. J. , Hark S. K. , Li Quan , Tang D. , Chu M. W. , Chen C. H.
Published: November 2006

Using combined microscopy and optical characterizations, the authors demonstrate effective Er doping into freestanding ZnO nanowires via ion implantation. The Er atoms are observed to take the substitutional sites in ZnO without causing obvious distortion to the host lattice. While the band gap threshold of the Er doped ZnO nanowires remains similar to that of the undoped ZnO, band tail states are created in the band structure of the ZnO upon Er doping. Room temperature 1.54μm emission is achieved in the doped nanowire sample after oxygen annealing. In particular, the generation of the band tail state(s) in the band gap of the ZnO nanowire host is found to be responsible for the 1.54μm emission under the below-band-gap indirect excitation.
Single carbon fiber as a sensing element in pressure sensors
Authors: Park C. S. , Kang B. S. , Lee D. W. , Choi Y. S.
Published: November 2006

The principal and innovative concept of this research is the replacement of piezoresistors in the current piezoresistive pressure sensors with carbon fibers. The piezoresistive characteristics of carbon fibers can play the same role as piezoresistors in current pressure sensors. The main structure of pressure sensors was built by back side etching on a silicon-on-insulator wafer to create a square diaphragm. Dielectrophoresis was used for the alignment and deposition of carbon fiber across the gap between two electrodes. The fabricated pressure sensors clearly showed linear response to applied pressure, so the feasibility of carbon-fiber-based pressure sensors was demonstrated.
Tunable negative refraction in nematic liquid crystals
Authors: Zhao Qian , Kang Lei , Li Bo , Zhou Ji , Tang Hong , Zhang Baizhe
Published: November 2006

A tunable negative refraction mechanism based on the properties of nematic liquid crystals is proposed. It shows that negative group refraction occurs at the interface between air and the nematic liquid crystals, and that the refraction can be adjusted by an applied electric field and by the temperature. For a nematic liquid crystal (E7, Merck), the group refraction is negative for the voltages of 1.0–2.8V and reaches a maximum at 1.5V. The negative group refraction decreases monotonously with increasing temperature. Such mechanism demonstrates the feasibility of tunable negative refraction devices based on liquid crystals.
Thermal stability of Pr silicate high-k layers on Si(001)
Authors: Lupina G. , Schroeder T. , Wenger Ch. , Dabrowski J. , Müssig H.-J.
Published: November 2006

Thermal stability of amorphous Pr silicate high-k layers on Si(001) was evaluated in view of complementary metal-oxide-semiconductor transistor processing requirements. Materials science techniques prove that no crystallization, no phase separation into SiO2 and Pr2O3, and no Pr silicide formation at the interface occur after 1min rapid thermal annealing treatment in N2 over the temperature range from 600to900°C. Electrical measurements confirm within this thermal budget well-behaved characteristics with k values between 11 and 13 and leakage currents about three orders of magnitude lower than in case of SiON reference layers.
Characterization of Pt∕SrBi2Ta2O9∕Hf–Al–O∕Si field-effect transistors at elevated temperatures
Authors: Li Qiu-Hong , Sakai Shigeki
Published: November 2006

Temperature dependence of electrical properties is studied statistically from 24 p-channel Pt∕SrBi2Ta2O9∕Hf–Al–O∕Si field-effect transistors up to 85°C. They show consistent properties and the distribution of threshold voltage is narrow. The memory window decreases from 1.40to1.15V as temperature increases from 27to85°C. Retention is characterized at zero bias voltage. The on-/off-state drain current ratios are above 105 at 27°C and nearly 104 at 85°C after more than 105s of measurement, respectively. These results are promising for future circuit integration of ferroelectric nonvolatile memories.
Field dependence of the magnetocaloric effect in materials with a second order phase transition: A master curve for the magnetic entropy change
Authors: Franco V. , Blázquez J. S. , Conde A.
Published: December 2006

The field dependence of the magnetic entropy change can be expressed as ΔSM∝Hn. For soft magnetic amorphous alloys n=1 well below the Curie temperature (TC), n=2 in the paramagnetic range, and n≈0.75 for T=TC. The first value can be explained with simple arguments, n=2 is a consequence of the Curie-Weiss law, but n(TC) deviates from mean field predictions. From the Arrott-Noakes equation of state, a relation between n(TC) and the critical exponents has been obtained, showing remarkable agreement with experimental data (for an example alloy, predicted n=0.72 versus experimental n=0.73). A master curve behavior for the temperature dependence of ΔSM measured for different maximum fields is proposed.
Room-temperature tunnel current amplifier and experimental setup for high resolution electronic spectroscopy in millikelvin scanning tunneling microscope experiments
Authors: le Sueur Hélène , Joyez Philippe
Published: December 2006

The spectroscopic resolution of tunneling measurements performed with a scanning tunneling microscope is ultimately limited by the temperature at which the experiment is performed. To take advantage of the potential high spectroscopic resolution associated with operating a scanning tunneling microscope in a dilution refrigerator we have designed a room-temperature tunnel current amplifier having very small back action on the tunnel contact and allowing to nearly reach the predicted energy resolution. This design is a modification of the standard operational amplifier based tip-biasing current-voltage converter which implements differential voltage sensing and whose back action on the tip voltage is only ∼2μV rms for a 14MV∕A transimpedance and 22kHz bandwidth.
Current-induced dynamics in asymmetric spin valves
Authors: Gmitra Martin , Barnaś Jozef
Published: November 2006

Spin transfer in an asymmetric nanopillar spin valve is studied numerically in the diffusive transport regime. The system considered includes a pinned synthetic antiferromagnetic structure, which is separated from the sensing layer by a thin nonmagnetic film. Landau-Lifshitz-Gilbert equation, with the spin-transfer torque taken into account, is used to study current-induced magnetic dynamics in the macrospin model. It is shown that steady dynamical states can occur in the absence of magnetic field. The advantage of systems including a synthetic antiferromagnetic structure, compared to simple spin valves, is also discussed.
Microplasma jet at atmospheric pressure
Authors: Hong Yong Cheol , Uhm Han Sup
Published: November 2006

A nitrogen microplasma jet operated at atmospheric pressure was developed for treating thermally sensitive materials. For example, the plasma sources in treatment of vulnerable biological materials must operate near the room temperature at the atmospheric pressure, without any risk of arcing or electrical shock. The microplasma jet device operated by an electrical power less than 10W exhibited a long plasma jet of about 6.5cm with temperature near 300K, not causing any harm to human skin. Optical emission measured at the wide range of 280–800nm indicated various reactive species produced by the plasma jet.
Observation of Fano asymmetry in Raman spectra of SrTiO3 and CaxSr1−xTiO3 perovskite nanocubes
Authors: Banerjee Sarbajit , Kim Dae-In , Robinson Richard D. , Herman Irving P. , Mao Yuanbing , Wong Stanislaus S.
Published: December 2006

Bulk SrTiO3 is cubic and not expected to exhibit any first-order Raman scattering. However, nanocubes of SrTiO3 with an edge length of 80±10nm show strong first-order Raman scattering originating from the breaking of symmetry caused by frozen surface dipoles (local tetragonality) and the presence of nanoscopic polar domains (arising from incorporated impurities). Rapid polarization fluctuations within these nanoscopic ferroelectric regions interfere with a polar phonon, resulting in a Fano-like asymmetric line shape in these SrTiO3 nanocubes, as well as in Ca0.3Sr0.7TiO3 nanocubes.
S
F
6
∕
O
2
plasma effects on silicon nitride passivation of AlGaN∕GaN high electron mobility transistors
Authors: Meyer David J. , Flemish Joseph R. , Redwing Joan M.
Published: December 2006

The effects of various plasma and wet chemical surface pretreatments on the electrical characteristics of AlGaN∕GaN high electron mobility transistors (HEMTs) passivated with plasma-deposited silicon nitride were investigated. The results of pulsed IV measurements show that samples exposed to various SF6∕O2 plasma treatments have markedly better rf dispersion characteristics compared to samples that were either untreated or treated in wet buffered oxide etch prior to encapsulation. The improvement in these characteristics correlates with the reduction of carbon on the semiconductor surface as measured with x-ray photoelectron spectroscopy. HEMT channel sheet resistance was also affected by varying silicon nitride deposition parameters.
Thermal diffusion behavior of hard-sphere suspensions
Authors: Ning Hui , Buitenhuis Johan , Dhont Jan K. G. , Wiegand Simone
Published: December 2006

We studied the thermal diffusion behavior of octadecyl coated silica particles (Rh=27nm) in toluene between 15.0 and 50.0°C in a volume fraction range of 1%–30% by means of thermal diffusion forced Rayleigh scattering. The colloidal particles behave like hard spheres at high temperatures and as sticky spheres at low temperatures. With increasing temperature, the obtained Soret coefficient ST of the silica particles changed sign from negative to positive, which implies that the colloidal particles move to the warm side at low temperatures, whereas they move to the cold side at high temperatures. Additionally, we observed also a sign change of the Soret coefficient from positive to negative with increasing volume fraction. This is the first colloidal system for which a sign change with temperature and volume fraction has been observed. The concentration dependence of the thermal diffusion coefficient of the colloidal spheres is related to the colloid-colloid interactions, and will be compared with an existing theoretical description for interacting spherical particles. To characterize the particle-particle interaction parameters, we performed static and dynamic light scattering experiments. The temperature dependence of the thermal diffusion coefficient is predominantly determined by single colloidal particle properties, which are related to colloid-solvent molecule interactions.
VvFT and VvMADS8, the grapevine homologues of the floral integrators FT and SOC1, have unique expression patterns in grapevine and hasten flowering in Arabidopsis
Authors: Sreekantan Lekha , Thomas Mark R.
Published: November 2006

The Vitis vinifera L. flowering genes VvFT and VvMADS8 from the grapevine cultivar Cabernet Sauvignon have been isolated. Sequence analyses showed that VvFT and VvMADS8 were highly homologous to the floral integrators, FLOWERING LOCUS T (FT) and SUPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1), respectively, from Arabidopsis. The expression pattern studied through real-time PCR revealed that expression of VvFT was quite low in axillary buds and high in developing inflorescence and berries. VvMADS8 was highly expressed in the axillary buds at the time when inflorescence primordia were being initiated in these buds suggesting that VvMADS8 is a gene involved in the early stages of inflorescence development. In tendrils, considered to be modified inflorescences, VvMADS8 was weakly expressed but high expression of VvFT in these organs showed that expression was irrespective of the flowering process. Through in situ hybridisation, strong expression of VvFT was detected in stamens and the ovary and ovule suggesting additional roles for VvFT in fruit and seed development. Strong expression of VvMADS8 was detected on the inflorescence primordium within the axillary bud. Overexpression of VvFT and VvMADS8 in Arabidopsis hastened flowering showing that both these genes function as promoters of flowering when ectopically expressed in a heterologous plant.
Root distributions of Australian herbaceous perennial legumes in response to phosphorus placement
Authors: Denton Matthew D. , Sasse Camille , Tibbett Mark , Ryan Megan H.
Published: November 2006

Many Australian plant species have specific root adaptations for growth in phosphorus-impoverished soils, and are often sensitive to high external P concentrations. The growth responses of native Australian legumes in agricultural soils with elevated P availability in the surface horizons are unknown. The aim of these experiments was to test the hypothesis that increased P concentration in surface soil would reduce root proliferation at depth in native legumes. The effect of P placement on root distribution was assessed for two Australian legumes, Kennedia prorepens F. Muell. and Lotus australis Andrews, and the exotic Medicago sativa L. Three treatments were established in a low-P loam soil: amendment of 0.15 g mono-calcium phosphate in either (i) the top 50 mm (120 µg P g–1) or (ii) the top 500 mm (12 µg P g–1) of soil, and an unamended control. In the unamended soil M. sativa was shallow rooted, with 58% of the root length of in the top 50 mm. K. prorepens and L. australis had a more even distribution down the pot length, with only 4 and 22% of their roots in the 0–50 mm pot section, respectively. When exposed to amendment of P in the top 50 mm, root length in the top 50 mm increased 4-fold for K. prorepens and 10-fold for M. sativa, although the pattern of root distribution did not change for M. sativa. L. australis was relatively unresponsive to P additions and had an even distribution of roots down the pot. Shoot P concentrations differed according to species but not treatment (K. prorepens 2.1 mg g–1, L. australis 2.4 mg g–1, M. sativa 3.2 mg g–1). Total shoot P content was higher for K. prorepens than for the other species in all treatments. In a second experiment, mono-ester phosphatases were analysed from 1-mm slices of soil collected directly adjacent to the rhizosphere. All species exuded phosphatases into the rhizosphere, but addition of P to soil reduced phosphatase activity only for K. prorepens. Overall, high P concentration in the surface soil altered root distribution, but did not reduce root proliferation at depth. Furthermore, the Australian herbaceous perennial legumes had root distributions that enhanced P acquisition from low-P soils.
Altering expression of the flavonoid 3′-hydroxylase gene modified flavonol ratios and pollen germination in transgenic Mitchell petunia plants
Authors: Lewis David , Bradley Marie , Bloor Stephen , Swinny Ewald , Deroles Simon , Winefield Chris , Davies Kevin
Published: November 2006

Antisense technology was successfully used to reduce flavonoid 3′-hydroxylase (F3′H) gene expression and enzyme activity and to promote the accumulation of monohydroxylated flavonols in petunia flower tissue. The hydroxylation pattern of specific flavonoid groups is a target for modification because of the possible associated changes in a range of factors including colour, stress tolerance and reproductive viability. Petunia (cv. Mitchell) plants were transformed to express in the antisense orientation the sequences encoding the F3′H (asF3′H). Transformants showed a range of responses, in terms of the level of endogenous F3′H gene expression and the relative proportion of the monohydroxylated flavonol (kaempferol) glycosides that accumulated. Kaempferol glycosides increased from 7% of the total flavonols in flower limb tissue of the wild type plants, to 45% in the flower limb tissue of line 114, the transgenic line that also showed the greatest decrease in F3′H expression in flower tissue. In leaf tissue, the trend was for a decrease in total flavonol concentration, with the relative proportion of kaempferol glycosides varying from ~40 to 80% of the total flavonols. The changes in leaf tissue were not consistent with the changes observed in flower tissue of the same lines. Endogenous F3′H activity in flower limb tissue was not completely shut down, although an 80% decrease in enzyme activity was recorded for line 114. The residual F3′H activity was still sufficient that quercetin glycosides remained as the major flavonol form. Alteration of F3′H activity appears to have affected overall flavonoid biosynthesis. A decrease in total flavonol concentration was observed in leaf tissue and two other flavonoid biosynthetic genes were down-regulated. No morphological changes were observed in the transgenic plants; however, up to a 60% decrease in pollen germination was observed in line 13. Thus, the relatively small change in flavonoid biosynthesis induced by the asF3′H transgene, correlated with several other effects beyond just the specific biosynthetic step regulated by this enzyme.
A synthetic phage λ regulatory circuit
Authors: Atsumi Shota , Little John W.
Published: November 2006

Analysis of synthetic gene regulatory circuits can provide insight into circuit behavior and evolution. An alternative approach is to modify a naturally occurring circuit, by using genetic methods to select functional circuits and evolve their properties. We have applied this approach to the circuitry of phage λ. This phage grows lytically, forms stable lysogens, and can switch from this regulatory state to lytic growth. Genetic selections are available for each behavior. We previously replaced λ Cro in the intact phage with a module including Lac repressor, whose function is tunable with small molecules, and several cis-acting sites. Here, we have in addition replaced λ CI repressor with another tunable module, Tet repressor and several cis-acting sites. Tet repressor lacks several important properties of CI, including positive autoregulation and cooperative DNA binding. Using a combinatorial approach, we isolated phage variants with behavior similar to that of WT λ. These variants grew lytically and formed stable lysogens. Lysogens underwent prophage induction upon addition of a ligand that weakens binding by the Tet repressor. Strikingly, however, addition of a ligand that weakens binding by Lac repressor also induced lysogens. This finding indicates that Lac repressor was present in the lysogens and was necessary for stable lysogeny. Therefore, these isolates had an altered wiring diagram from that of λ. We speculate that this complexity is needed to compensate for the missing features. Our method is generally useful for making customized gene regulatory circuits whose activity is regulated by small molecules or protein cofactors.
Developmental plasticity mirrors differences among taxa in spadefoot toads linking plasticity and diversity
Authors: Gomez-Mestre Ivan , Buchholz Daniel R.
Published: November 2006

Developmental plasticity is found in most organisms, but its role in evolution remains controversial. Environmentally induced phenotypic differences may be translated into adaptive divergence among lineages experiencing different environmental conditions through genetic accommodation. To examine this evolutionary mechanism, we studied the relationship between plasticity in larval development, postmetamorphic morphology, and morphological diversity in spadefoot toads, a group of closely related species that are highly divergent in the larval period and body shape and are distributed throughout temperate areas of both the New and the Old World. Previous studies showed that accelerated metamorphosis is adaptive for desert-dwelling spadefoot toads. We show that even under common garden conditions, spadefoot toad species show divergent reaction norms for the larval period. In addition, experimentally induced changes in the larval period caused correlated morphological changes in postmetamorphic individuals such that long larval periods resulted in relatively longer hindlimbs and snouts. A comparative analysis of morphological variation across spadefoot toad species also revealed a positive correlation between the larval period and limb and snout lengths, mirroring the effects of within-species plasticity at a higher taxonomic level. Indeed, after ≈110 Ma of independent evolution, differences in the larval period explain 57% of the variance in relative limb length and 33% of snout length across species. Thus, morphological diversity across these species appears to have evolved as a correlated response to selection for a reduced larval period in desert-dwelling species, possibly diverging from ancestral plasticity through genetic accommodation.
Mammalian pharmacokinetics of carbon nanotubes using intrinsic near-infrared fluorescence
Authors: Cherukuri Paul , Gannon Christopher J. , Leeuw Tonya K. , Schmidt Howard K. , Smalley Richard E. , Curley Steven A. , Weisman R. Bruce
Published: November 2006

Individualized, chemically pristine single-walled carbon nanotubes have been intravenously administered to rabbits and monitored through their characteristic near-infrared fluorescence. Spectra indicated that blood proteins displaced the nanotube coating of synthetic surfactant molecules within seconds. The nanotube concentration in the blood serum decreased exponentially with a half-life of 1.0 ± 0.1 h. No adverse effects from low-level nanotube exposure could be detected from behavior or pathological examination. At 24 h after i.v. administration, significant concentrations of nanotubes were found only in the liver. These results demonstrate that debundled single-walled carbon nanotubes are high-contrast near-infrared fluorophores that can be sensitively and selectively tracked in mammalian tissues using optical methods. In addition, the absence of acute toxicity and promising circulation persistence suggest the potential of carbon nanotubes in future pharmaceutical applications.
Genomewide screens for
Escherichia coli
genes affecting growth of T7 bacteriophage
Authors: Qimron Udi , Marintcheva Boriana , Tabor Stanley , Richardson Charles C.
Published: November 2006

Use of bacteriophages as a therapy for bacterial infection has been attempted over the last century. Such an endeavor requires the elucidation of basic aspects of the host–virus interactions and the resistance mechanisms of the host. Two recently developed bacterial collections now enable a genomewide search of the genetic interactions between
Escherichia coli
and bacteriophages. We have screened >85% of the
E. coli
genes for their ability to inhibit growth of T7 phage and >90% of the host genes for their ability to be used by the virus. In addition to identifying all of the known interactions, several other interactions have been identified.
E. coli
CMP kinase is essential for T7 growth, whereas overexpression of the
E. coli
uridine/cytidine kinase inhibits T7 growth. Mutations in any one of nine genes that encode enzymes for the synthesis of the
E. coli
lipopolysaccharide receptor for T7 adsorption leads to T7 resistance. Selection of T7 phage that can recognize these altered receptors has enabled the construction of phage to which the host is 100-fold less resistant.
MicroRNA-206 colocalizes with ribosome-rich regions in both the nucleolus and cytoplasm of rat myogenic cells
Authors: Ritland Politz Joan C. , Zhang Fan , Pederson Thoru
Published: November 2006

MicroRNAs are small, ≈21- to 24-nt RNAs that have been found to regulate gene expression. miR-206 is a microRNA that is expressed at high levels in
Drosophila
, zebrafish, and mouse skeletal muscle and is thought to be involved in the attainment and/or maintenance of the differentiated state. We used locked nucleic acid probes for
in situ
hybridization analysis of the intracellular localization of miR-206 during differentiation of rat myogenic cells. Like most microRNAs, which are presumed to suppress translation of target mRNAs, we found that miR-206 occupies a cytoplasmic location in cultured myoblasts and differentiated myotubes and that its level increases in myotubes over the course of differentiation, consistent with previous findings in muscle tissue
in vivo
. However, to our surprise, we also observed miR-206 to be concentrated in nucleoli. A probe designed to be complementary to the precursor forms of miR-206 gave no nucleolar signal. We characterized the intracellular localization of miR-206 at higher spatial resolution and found that a substantial fraction colocalizes with 28S rRNA in both the cytoplasm and the nucleolus. miR-206 is not concentrated in either the fibrillar centers of the nucleolus or the dense fibrillar component, where ribosomal RNA transcription and early processing occur, but rather is localized in the granular component, the region of the nucleolus where final ribosome assembly takes place. These results suggest that miR-206 may associate both with nascent ribosomes in the nucleolus and with exported, functional ribosomes in the cytoplasm.
Assessment of takotsubo (ampulla) cardiomyopathy using iodine-123 metaiodobenzylguanidine scintigraphy
Authors: Pessoa Pinheiro M. C. , Xavier Salles S. , Lima Souza Leão R. , Mansur J. , de Almeida Altino S. , Carvalho Pires A. C. , Gutfilen B. , da Fonseca Barbosa L. M.
Published: November 2006

Purpose: To evaluate the role of cardiac sympathetic innervation in patients whose clinical features consisted of chest pain, transient ST-segment elevation, left ventricular apical akinesis, minimal elevation of cardiac enzymes, and onset of symptoms shortly after a severe stress condition.

Material and Methods: Five female patients, mean age 67±14 years, underwent thoracic 123I-MIBG (planar and SPECT) and 67Ga citrate (planar) scans within 5 days after the onset of symptoms. The 123I-MIBG myocardial washout rate between early (30 min) and delayed (3 hours) planar images was calculated. All patients presented findings consistent with takotsubo-like syndrome. Echocardiograms showed the characteristic wall motion pattern of significant apical dysfunction. Acute-phase coronary angiographies revealed a non-obstructive pattern. A peculiar apical akinesis and basal normokinesis were observed on the ventriculograms.

Results: Impairment of cardiac neuronal uptake of 123I-MIBG based on a reduction of the heart-to-mediastinum uptake ratio was observed in all patients, while the washout rate was raised in four patients. All patients presented an apical uptake defect in the 123I-MIBG SPECT and planar images and a normal 67Ga scintigraphy.

Conclusion: Our data indicate that ampulla cardiomyopathy (AC) is associated with a cardiac sympathetic innervation deficit characterized by a reduced global 123I-MIBG uptake and an apical uptake defect. The lack of 67Ga uptake in the acute phase of this syndrome indicates that AC is probably not associated with an inflammatory process.
Role of magnetic resonance imaging in patient selection for uterine artery embolization
Authors: Cura M. , Cura A. , Bugnone A.
Published: November 2006

Uterine fibroids are common tumors of the female pelvis. Uterine artery embolization (UAE) is an effective treatment of symptomatic uterine leiomyoma in the appropriate candidates, reducing or eliminating leiomyoma-related symptoms of bleeding, bulk, and/or pain. Magnetic resonance imaging (MRI) can be used to assess women with symptoms potentially attributable to uterine leiomyomas, and help to determine who is an appropriate candidate for UAE. Because of soft tissue characterization, multiplanar imaging capabilities, and enhancement, MR imaging not only accurately detects and characterizes uterine leiomyomas but also may predict who will benefit from the embolization. MRI ability to detect coexistent uterine or pelvic pathology may change the diagnosis and treatment management of patients being evaluated for UAE.
Balloon occlusion test of the internal carotid artery: correlation with stump pressure and 99mTc-HMPAO SPECT
Authors: Kato K. , Tomura N. , Takahashi S. , Sakuma I. , Sasaki K. , Kitani H. , Watarai J.
Published: November 2006

Purpose: To evaluate the correlation of stump pressure during balloon occlusion test and relative cerebral blood flow (relative CBF) as measured by 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO) single-photon emission computed tomography (SPECT) after test occlusion.

Material and Methods: Balloon occlusion test of the internal carotid artery (ICA) was performed in 25 patients. The count ratio of occluded hemisphere to non-occluded hemisphere was calculated on 99mTc-HMPAO SPECT. The ratio of mean stump pressure to mean arterial pressure during carotid occlusion during the balloon occlusion test was compared with the count ratio of 99mTc-HMPAO SPECT.

Results: Two patients failed to tolerate even brief carotid occlusion. The other 23 patients showed no ischemic deficit during occlusion of the ICA. In 13 of these 23 patients, the ratios of mean stump pressure to mean arterial pressure were more than 50%, and the count ratios on SPECT were more than 85%. In 10 of 23 patients, the ratios of mean stump pressure to mean arterial pressure were less than 50%, and the count ratios on SPECT were variable.

Conclusion: Maintenance of a mean stump pressure of 50% or more of the mean systemic pressure during test occlusion indicates adequate cerebral blood flow during carotid occlusion.
Hepatic intra-arterial injection of 3-bromopyruvate in rabbit vx2 tumor
Authors: Shin S. W. , Han H. , Choo S. W. , Yoo B. C. , Park C. K. , Do Y. S. , Lee J. H. , Lee D. H. , Choi D. , Choo I.-W. , Kim S. S. , Lee J. Y.
Published: November 2006

Purpose: To evaluate the antitumoral effects of an intra-arterial injection of 3-bromopyruvate (3-BrPA) on liver VX2 tumor in rabbits.

Material and Methods: Twenty rabbits with surgically implanted liver VX2 tumors were used. The rabbits were divided into three groups: a control, a saline, and a 3-BrPA group. Four rabbits were not treated at all, and they served as the control group. The saline group ( n = 6) received only intra-arterial saline injection. The 3-BrPA group ( n = 10) received an intra-arterial injection of 3-bromopyruvate through the hepatic artery. The delivered amounts of 3-bromopyruvate were as follows: 25 ml of 0.5 mM in six rabbits, 25 ml of 1.0 mM in two rabbits, and 25 ml of 2.0 mM in two rabbits. Four days after intra-arterial injection, the rabbits were sacrificed and histopathologic analysis of the explanted livers was performed with comparison of the tumor necrosis ratio (a percentage of the necrotic area versus the entire tumorous area) in each group.

Results: The mean tumor necrosis ratio was 12.5±4.2%, 44.8±24.7%, and 49.4±14.3% in the control, saline, and 3-BrPA groups, respectively. Between the control and the saline group, and between the control and the 3-BrPA group the mean tumor necrosis ratio appeared to be significantly different ( P<0.05). However, there was no statistical difference in the mean tumor necrosis ratio between the saline and the 3-BrPA group ( P = 0.416).

Conclusion: A single session of intra-arterial injection of 3-BrPA showed no better results in terms of tumor necrosis than that of saline injection in a rabbit VX2 tumor model.
Misrepresentation of surface rendering of pediatric brain malformations performed following spatial normalization
Authors: Wallis L. I. , Widjaja E. , Wignall E. L. , Wilkinson I. D. , Griffiths P. D.
Published: November 2006

Purpose: To evaluate the effects of spatial normalization on volume rendering in cases of pediatric brain malformation.

Material and Methods: Three-dimensional (3D) T1-weighted volume datasets were acquired in three children, one with pachygyria, one with a Dandy-Walker malformation associated with polymicrogyria, and one with dysgenesis of the corpus callosum. On the non-normalized datasets, the skull margins were cropped and the remainder stripped with the brain extraction technique (BET). The data were also normalized into standard anatomic reference space using pediatric templates prior to the BET script. The surface constructions obtained by both techniques were then compared for geometric distortions.

Results: Normalization of 3D datasets resulted in significant distortions in the shape of the brain, with increased anterior–posterior dimensions and narrower transverse diameter in all three cases. In two cases, there were alterations in the appearance of the gyri and sulci, leading to a potential misinterpretation of the volume-rendered surface when the gyri and sulci were in fact normal.

Conclusion: In pediatric brain, particularly those with congenital brain anomalies, normalization as a post-processing step should be avoided as this may lead to misrepresentation of brain morphometry.
Preoperative portal vein embolization with a mixture of gelatin sponge and iodized oil: efficacy and safety
Authors: Kakizawa H. , Toyota N. , Arihiro K. , Naito A. , Fujimura Y. , Hieda M. , Hirai N. , Tachikake T. , Matsuura N. , Murakami Y. , Itamoto T. , Ito K.
Published: November 2006

Purpose: To evaluate whether portal vein embolization (PVE) using a mixture of gelatin sponge (GS) pieces and iodized oil is safe and effective in inducing hypertrophy of the future liver remnants (FLR).

Material and Methods: PVE was performed in 14 patients (eight male and six female, mean age 65 years, range 35–81 years) diagnosed with malignant liver tumor before surgery, whose FLR volumes were judged too small to allow for safe resection. Liver volume change, biochemical data change, complications related to PVE, and postoperative complications were retrospectively evaluated.

Results: PVE was successful in all patients, and there were no procedural complications. Absolute FLR volume and FLR/total liver volume (TLV) ratio increased by 102 cm3 and 8% (mean values), respectively. Planned hepatectomies were cancelled in three patients due to extrahepatic metastasis or bile duct infection. Five of the 11 patients (45%) who underwent hepatectomies had major postoperative complications. However, complications due to hepatic failure were not seen. In 10 patients, except one whose outcome was fatal outcome, the mean hospitalization days with and without major complications were 73 and 33 days, respectively.

Conclusion: PVE using a mixture of GS and iodized oil seems to be effective and safe in inducing hypertrophy of the FLR.
Magnetic resonance enteroclysis in the diagnosis of small-intestinal crohn's disease: diagnostic accuracy and inter- and intra-observer agreement
Authors: Negaard A. , Sandvik L. , Mulahasanovic A. , Berstad A. E. , Klöw N.-E.
Published: November 2006

Purpose: To evaluate the diagnostic accuracy and inter- and intra-observer agreement of magnetic resonance enteroclysis (MRE) in patients with or without Crohn's disease of the small intestine.

Material and Methods: 60 consecutive patients with or without Crohn's disease examined with MRE were included. Two observers independently reviewed the MRE examinations, searching for 12 pathological signs. The reference standard was ileoscopy or surgery of the terminal ileum performed in 41 patients.

Results: Crohn's disease of the small intestine was found in 24 (40%) patients. MRE findings of increased intestinal wall thickness, intestinal wall enhancement, intestinal wall ulcer, and inflammatory activity of the terminal ileum showed high sensitivity, specificity, and positive and negative predictive values. Intestinal stenosis had sensitivities ranging from 43% to 100%, depending on the cut-off value. Inter- and intra-observer agreement was good or excellent for most pathological signs. However, observer agreement of intestinal wall edema was only fair and moderate.

Conclusion: MRE evaluated Crohn's disease with a high diagnostic accuracy in the terminal ileum. Most MRE variables were evaluated with good or excellent observer agreement, indicating that the method was highly reproducible. Our study supports the notion that MRE is an appropriate method for diagnosing Crohn's disease.
Increased sensitivity to pathological brain changes using co-registration of magnetic resonance imaging scans
Authors: Burdett J. , Stevens J. , Flügel D. , Williams E. , Duncan J. S. , Lemieux L.
Published: November 2006

Purpose: To compare automatic software-based co-registration of serial magnetic resonance imaging (MRI) scans with conventional visual comparison, by expert neuroradiologists.

Material and Methods: Sixty-four patients who were referred to our epilepsy MRI unit for cerebral imaging were identified as having potentially, non-, or slow-growing lesions or cerebral atrophy and followed with sequential scans over a period of up to 8 years, resulting in a total of 92 pairs of scans. Scans were categorized as showing either lesions or atrophy. Each pair of scans was reviewed twice for the presence of change, with and without co-registration, performed using automated software.

Results: Co-registration and visual reporting without co-registration were discordant in the lesions group in nine out of 69 datasets (13%), and in 16 out of 23 pairs of scans in the atrophy group (69%). The most common cause of discordance was visual reporting not detecting changes apparent by co-registration. In three cases, changes detected visually were not detected following co-registration.

Conclusion: In the group of patients studied, co-registration was more sensitive for detecting changes than visual comparison, particularly with respect to atrophic changes of the brain. With the increasing availability of sophisticated independent consoles attached to MRI scanners that may be used for image co-registration, we propose that serial T1-weighted volumetric MRI brain co-registration should be considered for integration into routine clinical practice to assess patients with suspected progressive disease.
Sequential dynamic gadolinium magnetic resonance perfusion-weighted imaging: effects on transit time and cerebral blood volume measurements
Authors: Griffiths P. D. , Pandya H. , Wilkinson I. D. , Hoggard N.
Published: November 2006

Purpose: To evaluate if two gadolinium perfusion studies can be performed during the same table occupancy without degradation of the derived data in the second study.

Material and Methods: Magnetic resonance (MR) perfusion studies of the whole brain were performed on 12 patients during the administration of two gadolinium boluses separated by 8 min. In six patients, gadolinium was given as two 20-ml administrations of standard 0.5 M chelate (Magnevist), whilst the other six patients received two 10-ml administrations of 1.0 M chelate (Gadovist).

Results: There were no significant differences in subjective quality between the time–intensity curves of the first and second perfusion studies using either the 0.5 M or 1.0 M gadolinium chelate. The objective measurements in quality of the time–intensity curves (maximum signal change and full width at half maximum) changed by less than 5% of the original values on the second perfusion study. The first-moment mean transit times did not change significantly on the sequential studies. The regional cerebral blood volume tended to increase on the second study (by 15% on average), but this did not reach statistical significance.

Conclusion: The results from two sequential dynamic gadolinium-based perfusion studies can be compared in a meaningful manner using the technique described.
Diffusion-weighted magnetic resonance imaging of treatment-associated changes in recurrent and residual medulloblastoma: preliminary observations in three children
Authors: Schubert M. I. , Wilke M. , Müller-Weihrich S. , Auer D. P.
Published: November 2006

Purpose: To emphasize a possible role of magnetic resonance (MR) diffusion-weighted imaging (DWI) for lesion conspicuity and detection of treatment effects in children with medulloblastoma.

Material and Methods: Three children with medulloblastoma (two residual and one recurrent) were examined repetitively by MR diffusion-weighted imaging. Regional assessment of the apparent diffusion coefficient (ADC) was done for tumorous lesions and periventricular white matter appearing normal on standard MR images.

Results: All lesions were clearly visible on DWI. In the case of recurrent tumor, on one scan, DWI showed lesions that were not seen on contrast-enhanced MRI. Increase (41%) of ADC was seen in one lesion, which subsequently responded completely to treatment over 27 months' follow-up. Intermediate increases (23–26%) of ADC were found with partial therapy response in three lesions. In contrast, a decrease (-11%) of ADC in two lesions was seen with tumor progression.

Conclusion: These observations may suggest a role for DWI in early detection of metastatic disease and treatment monitoring of medulloblastoma, warranting a formal study.
Atypical imaging findings of infantile hemangioendothelioma: a case report
Authors: Mavili E. , Kahriman G. , Tuna I. S. , Coskun A.
Published: November 2006

Infantile hemangioendothelioma is the third most common hepatic tumor in children, and the most common benign vascular tumor of the liver in infancy. On computed tomography (CT) and magnetic resonance imaging (MRI), typical enhancement patterns similar to those seen in adult hemangiomas may help establish the diagnosis. However, atypical enhancement patterns may also occur. In this paper, we report a rare form of solitary infantile hemangioendothelioma that showed a rim-like calcification and rim-like enhancement on CT and MRI.
Does mastering have an effect on disability pensioning independent of health, and may it explain divides of education in the Oslo Health Survey?
Authors: Valset Kirsti , Naper Sille Ohrem , Claussen Bjørgulf , Dalgard Odd Steffen
Published: November 2006

Aims: Does mastering abilities have an independent effect on disability pensioning? Are some of the large divides across education explained by mastering factors when adjusted for health? Methods: Data from the National Insurance Administration were linked to a health survey of 10,720 Oslo inhabitants aged 40, 45, and 60 years, 46% of the total populations in these age groups who were invited to a Health Survey in 2000—01. Measures of general health, chronic somatic diseases, psychiatric symptoms, and musculoskeletal pain were self-reported. The mastering test Generalized Self Efficacy was used. Results: 10.5% of our eligible sample had disability pension at the time of the survey. The risk was more than five times higher for those with primary school than for those with university education and 50% higher for women than for men. Lowest score on the Generalized Self Efficacy test (poor mastering) had an age-, gender-, and health-adjusted OR of 2.4 compared with the highest level of mastering. Adjusting for mastering lowered the educational divide but not that of gender, when health indicators were taken into consideration Those reporting poor general health had a seven times higher risk than those with good health, and those with a chronic somatic disease, musculoskeletal pain, or poor psychiatric health had a somewhat lower increase in risk of disability pension. Health measures did reduce the impact of education, but not of gender, when adjusted for mastering. Conclusion: Poor mastering was associated with disability pensioning, and reduced the differences across educational level and health but not across gender.