bluuebunny/crossref_metadata_2025 huggingface dataset:
Methyltrimethoxysilane-insulated piezoelectric microcantilevers for direct, all-electrical biodetection in buffered aqueous solutions
Authors: Capobianco Joseph A. , Shih Wan Y. , Shih Wei-Heng
Published: December 2006

We have examined coating (PbMg1∕3Nb2∕3O3)0.63–(PbTiO3)0.37 (PMN-PT)/tin piezoelectric microcantilever sensors (PEMSs) with a thin methyltrimethoxysilane (MTMS) by a simple solution method to electrically insulate the PEMS for biodetection in phosphate buffered saline (PBS) solutions. The PMN-PT/tin PEMSs were constructed using PMN-PT freestanding films that exhibited an electric-field-enhanced giant piezoelectric coefficient. The insulation procedure involved spin coatings of MTMS followed by cross-linking in water, which yielded a coating layer of about 10nm in thickness on the tin side of the PEMS. We showed that the MTMS-insulated PMN-PT/tin PEMSs were capable of electrical self-excitation and self-sensing with a stable resonance spectrum exhibiting a quality factor of Q=50 when submerged in 0.1M PBS solution. Direct, all-electrical, in situ detection of Escherichia coli O157:H7 at various concentrations was demonstrated at a flow rate of 0.5ml∕min. A MTMS-insulated PMN-PT/tin PEMS 725μm long consisting of a 22-μm-thick PMN-PT layer and a 6-μm-thick tin layer exhibited a mass detection sensitivity Δm∕Δf=−3±2×10−12g∕Hz and a concentration sensitivity of better than 100cells∕ml in less than 1ml of liquid.
Competitive bond breaking in floppy molecular trimers: HeNeH and HeNeH− calculations
Authors: Orlandini S. , Baccarelli I. , Gianturco F. A.
Published: December 2006

Calculations for the J=0 bound states associated with the two title molecular systems are carried out using distributed Gaussian function approach and using the sum of two-body potential approximation to describe the overall interactions. The results yield one bound state for the neutral trimer and three bound states for the anionic triatom. The relative values of dissociation energies place the first dissociation threshold at the H emission for the neutral complex and at the He emission for the corresponding anion. The general spatial properties of the various bound states are analyzed on both systems.
Simultaneous measurement of electric birefringence, light scattering, and electric current for liquid systems
Authors: Alessi M. , Zothner E. , Acosta E. , Bisceglia M.
Published: December 2006

In this work we present an experimental setup that allows measuring, simultaneously, the electric birefringence, the electric light scattering, and the cell electrical current under the action of an external electric field. The basic design corresponds to a standard birefringence setup. The Kerr cell was built to permit the observation of 90° light scattering. The high voltage pulse generator is used to measure the electrical current across the Kerr cell. We present experimental data, taken in colloidal systems with different electrical conductivities.
Raman study across Verwey transition of epitaxial Fe3O4 thin films on MgO (100) substrate grown by pulsed laser deposition
Authors: Phase D. M. , Tiwari Shailja , Prakash Ram , Dubey Aditi , Sathe V. G. , Choudhary R. J.
Published: December 2006

We present a Raman study of Fe3O4 (100) thin films across the Verwey transition in the temperature range of 85–300K. These films are epitaxially grown on MgO (100) substrate by pulsed laser deposition technique. X-ray diffraction and low temperature resistivity measurements reveal that these films exhibit high structural order and perfect stoichiometry with Verwey transition at 121K. The frequency of different Raman modes [A1g and T2g(2)] changes abruptly around the Verwey transition temperature (TV). Below TV we observe a splitting in T2g(3) mode. Using Allen’s formula [Solid State Commun. 14, 937 (1974)] the strength of the electron-phonon coupling (λ) is estimated from the observed line shape parameters, and our estimates show that in epitaxially grown Fe3O4 thin films strong electron-phonon coupling is present. This coupling parameter is larger for T2g(3) mode as compared with that of A1g and T2g(2) modes. It is also observed that the coupling parameter corresponding to A1g mode remains invariant going from bulk single crystal to thin film while that of T2g(2) and T2g(3) modes are almost doubled. An attempt has been made to correlate the observed behavior with the presence of antiphase boundary in epitaxial thin films.
Testing the TPSS meta-generalized-gradient-approximation exchange-correlation functional in calculations of transition states and reaction barriers
Authors: Kanai Yosuke , Wang Xiaofei , Selloni Annabella , Car Roberto
Published: December 2006

We have studied the performance of local and semilocal exchange-correlation functionals [meta-generalized-gradient-approximation (GGA)-TPSS, GGA–Perdew-Burke-Ernzerhof (PBE), and local density approximation (LDA)] in the calculation of transition states, reaction energies, and barriers for several molecular and one surface reaction, using the plane-wave pseudopotential approach. For molecular reactions, these results have been compared to all-electron Gaussian calculations using the B3LYP hybrid functional, as well as to experiment and high level quantum chemistry calculations, when available. We have found that the transition state structures are accurately identified irrespective of the level of the exchange-correlation functional, with the exception of a qualitatively incorrect LDA prediction for the H-transfer reaction in the hydrogen bonded complex between a water molecule and a OH radical. Both the meta-GGA-TPSS and the GGA-PBE functionals improve significantly the calculated LDA barrier heights. The meta-GGA-TPSS further improves systematically, albeit not always sufficiently, the GGA-PBE barriers. We have also found that, on the Si(001) surface, the meta-GGA-TPSS barriers for hydrogen adsorption agree significantly better than the corresponding GGA-PBE barriers with quantum Monte Carlo cluster results and experimental estimates.
Single-photon detection using a quantum dot optically gated field-effect transistor with high internal quantum efficiency
Authors: Rowe M. A. , Gansen E. J. , Greene M. , Hadfield R. H. , Harvey T. E. , Su M. Y. , Nam S. W. , Mirin R. P. , Rosenberg D.
Published: December 2006

We investigate the operation of a quantum dot, optically gated, field-effect transistor as a photon detector. The detector exhibits time-gated, single-shot, single-photon sensitivity, a linear response, and an internal quantum efficiency of up to (68±18)% at 4K. Given the noise of the detector system, they find that a particular discriminator level can be chosen so the device operates with an internal quantum efficiency of (53±11)% and dark counts of 0.003 counts per shot.
Origin of deep level defect related photoluminescence in annealed InP
Authors: Zhao Youwen , Dong Zhiyuan , Miao Shanshan , Deng Aihong , Yang Jun , Wang Bo
Published: January 2007

Deep level defects in annealed InP have been studied by using photoluminescence spectroscopy (PL), thermally stimulated current (TSC), deep level transient spectroscopy (DLTS), and positron annihilation lifetime (PAL). A noticeable broad PL peak centered at 1.3eV has been observed in the InP sample annealed in iron phosphide ambient. Both the 1.3eV PL emission and a defect at EC−0.18eV correlate with a divacancy detected in the annealed InP sample. The results make a divacancy defect and related property identified in the annealed InP.
Simple liquid-core waveguide polarimetry
Authors: Preston Thomas C. , Jones Nathan D. , Stille Sven , Mittler Silvia
Published: December 2006

A simple, low cost, liquid-core waveguide polarimeter is presented. The rotation of polarized light was measured after passing through a hollow fiber containing the chiral solution of interest. Sensitivity was found to scale with fiber length. For compactness, the fiber can be curled into a right-angle figure 8 configuration and this eliminated any phase effects that would otherwise be introduced. The limit of detection was 0.3mM for both (S)-(−)-limonene and (R)-(+)-limonene using a 220.8cm long fiber with a run time of approximately 30s and a core volume of 38.9μl.
Three-dimensional gas temperature measurements in atmospheric pressure microdischarges using Raman scattering
Authors: Belostotskiy Sergey G. , Wang Qiang , Donnelly Vincent M. , Economou Demetre J. , Sadeghi Nader
Published: December 2006

Spatially resolved three-dimensional rotational Raman spectroscopy of ground state nitrogen was used to measure the gas temperature (Tg) in a normal dc glow microdischarge (300μm gap between 0.5×0.05mm2 parallel electrodes) in pure N2. An original backscattering confocal optical system with a spatial resolution of ∼40μm was developed for collecting Raman spectra. Gas temperatures were measured at several points across the gap as well as along the axis perpendicular to the discharge plane. Tg peaked near the cathode and was 1200K in the negative glow of a 500Torr, 20mA discharge.
Effects of chromophore orientation and molecule conformation on surface-enhanced Raman scattering studied with alkanoic acids and colloidal silver nanoparticles
Authors: Seballos Leo , Olson Tammy Y. , Zhang Jin Z.
Published: December 2006

Experimental studies have been carried out to gain a better understanding of the effects of chromophore orientation and molecular conformation on surface-enhanced Raman scattering (SERS) based on metal nanostructures. A series of alkanoic acids that contain a phenyl ring separated by methylene groups from the carboxylic acid, including phenylacetic acid, 3-phenylpropionic acid, 4-phenylbutyric acid, 5-phenylvaleric acid, and 6-phenylhexanoic acid, was investigated as model molecules with colloidal silver nanoparticles as SERS substrates. As the number of methylene groups increases, the molecules display an interesting zigzag intensity pattern of the phenyl ring bending mode around 1000cm−1 as well as a trend of appearance and disappearance of either the degenerate ring breathing mode or CO vibrational mode near 1585 and 1630cm−1, respectively. Molecules containing an odd number of methylene units display a higher ring bending intensity and degenerate ring breathing mode and are suggested to have a trans conformation on the particle surface. Molecules with an even number of methylene units show a CO vibrational mode and weaker ring bending in their SERS spectra and are suggested to have a gauche conformation on the silver nanoparticle surface. The different conformation is attributed to the varying interactions of the carboxylic group or the phenyl ring π electrons with the silver surface. The SERS intensity was found to change little as the length between the phenyl ring and the carboxylic group was increased by adding CH2 spacers. This is possibly because the effective distance between the phenyl ring and the silver surface does not change much with increasing number of CH2 spacers as a result of changes in molecular conformation and variations in the phenyl ring orientation with CH2 addition. The insight gained from this study is important for understanding SERS of complex molecules for which chromophore orientation and molecular conformation must be taken into careful consideration.
Critical transition for the edge shear layer formation: Comparison of model and experiment
Authors: Carreras B. A. , Garcia L. , Pedrosa M. A. , Hidalgo C.
Published: December 2006

The experimental results for the emergence of the plasma edge shear flow layer in TJ-II [C. Alehaldre et al.Fusion Technol. 17, 131 (1990)] can be explained using a simple model for a second-order transition based on the sheared flow amplification by Reynolds stress and turbulence suppression by shearing. In the dynamics of the model, the resistive interchange instability is used. This model gives power dependence on density gradients before and after the transition, consistent with experiment.
Color tunable organic light-emitting diodes by using europium organometallic complex
Authors: Liang C. J. , Choy Wallace C. H.
Published: December 2006

Using the rare-earth special feature of a sharp emission spectrum, voltage-controlled continuous color tuning of organic light-emitting diodes is achieved. Europium(dibenzoylmethanato)3(bathophenanthroline) is used as the strategic starting point close to the red corner of the Commission International de I’Eclairage chromaticity diagram for a wide color tuning. The end point and path of the color tuning can be engineered by doping the hole-transport emitting layer with dyes. The mechanisms of color tuning have been investigated and explained by the efficiency reduction of the europium complex and the extension of carrier recombination zone with driving voltage. The effect of exciplex on the color tuning is also studied.
Efficient formulation and computer implementation of the active-space electron-attached and ionized equation-of-motion coupled-cluster methods
Authors: Gour Jeffrey R. , Piecuch Piotr
Published: December 2006

The efficient, general-purpose implementations of the active-space electron-attached (EA) and ionized (IP) equation-of-motion coupled-cluster (EOMCC) methods including up to 3p-2h and 3h-2p excitations, called EA-EOMCCSDt and IP-EOMCCSDt, respectively, are discussed. The details of the algorithm that enables one to achieve a high degree of code vectorization for the active-space methods and the factorized forms of the EA- and IP-EOMCCSDt equations that maximize the benefits of using active orbitals in the process of selecting the dominant 3p-2h and 3h-2p excitations are presented. The results of benchmark calculations for the low-lying doublet and quartet states of the CH and SH radicals reveal that the active-space EA-EOMCCSDt and IP-EOMCCSDt methods are capable of producing results for the electronic excitations in open-shell systems that match the high accuracy of EA- and IP-EOMCC calculations with a full treatment of 3p-2h and 3h-2p excitations, even when the excited states of interest display a manifestly multideterminantal nature, with the costs that can be on the same order of those characterizing the basic EOMCC singles and doubles approach.
Highly efficient deep blue organic electroluminescent device based on 1-methyl-9,10-di(1-naphthyl)anthracene
Authors: Ho Meng-Huan , Wu Yao-Shan , Wen Shih-Wen , Lee Meng-Ting , Chen Teng-Ming , Chen Chin H. , Kwok Kwong-Chau , So Shu-Kong , Yeung Kai-Tai , Cheng Yuen-Kit , Gao Zhi-Qiang
Published: December 2006

The author have developed 2-methyl-9,10-di(1-naphthyl)anthracene (α,α-MADN) as an effective wide band gap host material for Förster energy transfer to the unsymmetrical mono(styryl)amine deep blue fluorescent dopant (BD-1). This guest/host emitting system, at the optimal doping concentration of 3%, can also increase the probability of carrier recombination near the hole-transport/emitting layer interface for the blue organic light emitting device which produces electroluminescence efficiencies of 3.3cd∕A and 1.3lm∕W and a deep blue CIEx,y color coordinates of (0.15, 0.13) that are 50% better than those of the traditional β,β-isomeric host (MADN) with the same dopant.
Plasma wave detection of terahertz radiation by silicon field effects transistors: Responsivity and noise equivalent power
Authors: Tauk R. , Teppe F. , Boubanga S. , Coquillat D. , Knap W. , Meziani Y. M. , Gallon C. , Boeuf F. , Skotnicki T. , Fenouillet-Beranger C. , Maude D. K. , Rumyantsev S. , Shur M. S.
Published: December 2006

Si metal oxide semiconductor field effect transistors (MOSFETs) with the gate lengths of 120–300nm have been studied as room temperature plasma wave detectors of 0.7THz electromagnetic radiation. In agreement with the plasma wave detection theory, the response was found to depend on the gate length and the gate bias. The obtained values of responsivity (⩽200V∕W) and noise equivalent power (⩾10−10W∕Hz0.5) demonstrate the potential of Si MOSFETs as sensitive detectors of terahertz radiation.
Contact epitaxy in multiple cluster deposition
Authors: Meinander K. , Järvi T. T. , Nordlund K.
Published: December 2006

The specific properties of cluster-assembled thin films depend heavily on the size of deposited clusters as well as the energy with which they impact the substrate. When depositing at thermal energies, small enough clusters will align completely epitaxially with a smooth substrate, whereas larger clusters may form structures containing grains. As more clusters are deposited, however, they will no longer impact on a smooth surface, but rather on a surface roughened by previously deposited clusters. Using molecular dynamics simulations, the authors have determined the upper limit in cluster size for epitaxial deposition of multiple copper clusters at temperatures ranging from 0to750K.
Relationship between indium tin oxide surface treatment and hole injection in C60 modified devices
Authors: Kim Sung Hyun , Jang Jyongsik , Lee Jun Yeob
Published: December 2006

The effect of indium tin oxide (ITO) surface treatment on hole injection in organic light-emitting diode with C60 as a buffer layer on ITO was studied. Double surface dipole layer was induced on oxygen plasma treated ITO surface, while no dipole formation was observed on ITO without surface treatment. Interfacial energy barrier between ITO and hole transport layer was reduced by 0.4eV by C60 modification on oxygen plasma treated ITO surface, while there was no change of interfacial energy barrier by C60 on ITO without surface treatment.
Organic-transistor-based flexible pressure sensors using ink-jet-printed electrodes and gate dielectric layers
Authors: Noguchi Yoshiaki , Sekitani Tsuyoshi , Someya Takao
Published: December 2006

The authors have fabricated 33cm diagonal flexible pressure sensors using organic field-effect transistor (FET) active matrices. Polyimide precursors and silver nanoparticles are patterned on a polyimide film by using an ink-jet printing system and cured at 180°C to form gate dielectric layers and electrodes for organic FETs, respectively. In order to define the device dimensions, epoxy partitions are prepared by a screen printing system. The mobility of the transistors is 0.7cm2∕Vs and the on/off ratio exceeds 106. Spatial distributions of pressure are read out by an organic FET active matrix.
Au wetting and nanoparticle stability on GaAs(111)B
Authors: Hilner E. , Mikkelsen A. , Eriksson J. , Andersen J. N. , Lundgren E. , Zakharov A. , Yi H. , Kratzer P.
Published: December 2006

Au nanoparticles and Au films for growth of nanowires on the GaAs(111)B surface have been studied by a combination of experimental and theoretical techniques. If Au is present in either form, annealing to temperatures relevant for nanowire growth results in the formation of a thin Au wetting layer. Based on density functional theory calculations and experimental data, a structural model is proposed with an Au atom on every third threefold hollow hcp site of the Ga lattice. The authors observe that the stability of Au nanoparticles is governed by the presence of the wetting layer and outdiffusion of Au from the nanoparticles.
Programable molecular orbital states of C60 from integrated circuits
Authors: Hou Tuo-Hung , Ganguly Udayan , Kan Edwin C.
Published: December 2006

The authors have reported experimental demonstration of four C60 programable molecular orbital states, C600, C601−, C602−, and C603−, through a charge-based nonvolatile memory cell. Owing to the monodisperse nature and molecular size of C60, very sharp Coulomb staircase is observed at room temperature. A physical model based on the molecular orbit structure, the charging energy solved by an electrostatic method, and the Fermi-level pinning theory yield good quantitative agreement with experiments. These not only lead to better understanding of the C60 molecular orbital structure and corresponding chemical redox levels, but also potentially pave the way for realizing reliable multilevel molecular memories.
Comparison of carrier dynamics in GaN quantum dots and GaN quantum wells embedded in low-Al-content AlGaN waveguides
Authors: Cho Yong-Hoon , Kwack H. S. , Kwon B. J. , Barjon J. , Brault J. , Daudin B. , Dang Le Si
Published: December 2006

Comparative analysis of the carrier dynamics of GaN quantum dot (QD) and GaN quantum well (QW) separated confinement heterostructures (SCHs) with low-Al-content AlGaN waveguide layers is reported. A redshift (blueshift) of QD (wetting layer) emission is found with respect to QW emission, as expected from the thickness hierarchy of these objects. The influence of nonradiative processes on QD emission in QD SCH is dramatically reduced compared to the case of QW SCH. It is concluded that GaN QDs in low-Al-content AlGaN matrix are robust localization centers and that the carrier dynamics is seriously affected by the built-in internal field effect.
Direct noninterference cylindrical vector beam generation applied in the femtosecond regime
Authors: Moh K. J. , Yuan X.-C. , Bu J. , Low D. K. Y. , Burge R. E.
Published: December 2006

This letter describes the generation of femtosecond cylindrical vector beams by passing the optical pulse through a microfabricated spiral phase plate and an azimuth-type polarization analyzer. The resulting beam resembles a doughnut and has a polarization that is axially symmetric. Portions of the wave front were sampled via the GRENOUILLE frequency resolved optical grating device; it was found that the original pulse of 200fs was stretched slightly by ∼13fs. Compared to an interferometric beam combination technique, this experiment geometry is simple, minimizes material dispersion, and has negligible spatial chirp.
Infrared emission from Ge metal-insulator-semiconductor tunneling diodes
Authors: Liao M. H. , Cheng T.-H. , Liu C. W.
Published: January 2007

The Ge light-emitting diode with ∼1.8μm strong infrared emission is demonstrated using a metal-insulator-semiconductor tunneling structure. The intensity of a Ge device is one order of magnitude stronger than a similar Si device. At the positive gate bias, the holes in the Al gate electrode tunnel to the n-type Ge through the ultrathin oxide and recombine radiatively with electrons. An electron-hole-plasma model can be used to fit all the emission spectra from room temperature down to 65K. From the measurement temperature range, the extracted band gap is ∼40meV lower than the reported band gap data, and the linewidth drops from 70to25meV. The longitudinal acoustic phonon (∼28meV) and/or the band gap renormalization at high carrier density are proposed to be responsible for the reduction of photon energy. The band gap reduction on the mechanically strained n-type Ge and Si is also investigated experimentally and theoretically.
Temperature dependence of intrinsic switching current of a Co nanomagnet
Authors: Yang T. , Hirohata A. , Hara M. , Kimura T. , Otani Y.
Published: December 2006

The temperature dependence of the switching current of a magnetic nanopillar is investigated from 10to290K. According to the switching probability measurement with the pulsed current, and the differential resistance measurement with sweeping the dc current, the intrinsic switching currents increase with decreasing the temperature. Transport calculations show that this temperature dependence is closely related to the reduced spin accumulation and spin polarization of the electrical current at low temperatures, attributed to the varied transport parameters. The conclusion is in accordance with the temperature dependence of the resistance difference between antiparallel and parallel magnetic configurations.
Enhanced electron field emission from preferentially oriented graphitic films
Authors: Shpilman Z. , Philosoph B. , Kalish R. , Michaelson Sh. , Hoffman A.
Published: December 2006

The electron field emission properties of nanographite films, whose basal planes display a degree of preferred orientation perpendicular to the surface, are reported. It was found that nanometric thick films which display a high degree of preferred orientation perpendicular to the substrate emit electrons at a high turn on field (TOF), while thicker films which display a much lower degree of preferred orientation emit electrons at a significantly lower TOF. It is suggested that the observed effect is mainly associated with the degree of basal planes orientation of the nanostructures and not just to their length.
Optical isolating action in surface plasmon polaritons
Authors: Khurgin Jacob B.
Published: December 2006

The authors consider propagation of a plasmon polariton on the interface between a metal and a magneto-optical material and show that in presence of transverse magnetic field a strong nonreciprocal phase shift results. This phenomenon can be used to achieve optical isolation action in short nanoplasmonic guides with low insertion loss.
Doping and defects in the formation of single-crystal ZnO nanodisks
Authors: Qi Junjie , Zhang Yue , Huang Yunhua , Liao Qingliang , Liu Juan
Published: December 2006

High purity growth of polar surface dominated ZnO nanodisks was fabricated by introducing In ions in the raw material by thermal evaporation process without a catalyst. The nature of the sharp-contrast lines in the disks was investigated. The results suggested that the existence of sharp-contrast lines is due to the local segregation of In. Defects were initiated by segregation of the doping element of indium, which reduced the surface energy of ZnO (0001) leading to the fastest growth of the nanodisks along ⟨011¯0⟩. The preferred growth along ⟨011¯0⟩ is considered to maximize the effect of the piezoelectricity.
Refined calculations of effective attenuation lengths for SiO2 film thicknesses by x-ray photoelectron spectroscopy
Authors: Powell C. J. , Werner W. S. M. , Smekal W.
Published: December 2006

Electron effective attenuation lengths (EALs) for SiO2 films on Si are reported that were obtained from Monte Carlo simulations of substrate Si 2p3∕2 photoelectron transport for x-ray photoelectron spectroscopy (XPS) with AlKα and MgKα x rays and SiO2 films of varying thicknesses. These EALs show a stronger dependence on SiO2 thickness than previous values found from an approximate algorithm. Since recent XPS data for SiO2 can be analyzed satisfactorily with thickness-independent EALs, the results indicate that intrinsic excitations and/or variations of inelastic-scattering probabilities near surfaces and interfaces appear to be significant in quantitative XPS.
Mobility spatial distribution function: Comparative method for conjugated polymers/molecules
Authors: Rappaport Noam , Bar Yehoram , Solomeshch Olga , Tessler Nir
Published: December 2006

The authors report improved method for extracting mobility spatial distribution function that accounts for the finite light-absorption depth. They employ step function light excitation and use the photocurrent temporal response to extract the electrons’ mobility spatial distribution function (MDF). This directly measures the relevant electronic disorder in amorphous conjugated polymers. Comparing two different polymers shows that qualitative analysis of field effect transistor data is in good agreement with the quantitative analysis provided by the MDF concept/method. The better uniformity of the electronic properties found in green polypnenylene vinylene is a clear indication for its better performance and lifetime.
Organosilane functionalization of InN surface
Authors: Chen Chi-Fan , Wu Chung-Lin , Gwo Shangjr
Published: December 2006

Direct coupling of aminosilane molecules onto the plasma hydroxylated InN surface is demonstrated. By using synchrotron-radiation photoelectron spectroscopy, the authors have studied the surface chemical properties of (3-aminopropyl)trimethoxysilane coupled InN. They have also found that the positively charged amine terminal groups on the functionalized InN surface can be utilized to bind negatively charged Au colloids (10nm diameter) in aqueous solution. Combining with the existing bioconjugation techniques for Au colloids, this approach opens up the possibility of nanoparticle-biomolecular hybrid systems for chemical and biosensing using electronic devices based on surface-functionalized InN.
Large-scale dynamics in two-dimensional Euler and surface quasigeostrophic flows
Authors: Tran Chuong V. , Dritschel David G.
Published: December 2006

The large-scale dynamics in classical two-dimensional Euler and surface quasigeostrophic flows are studied by examining the evolution of the mean-square stream function ⟨ψ2⟩ and of the Fourier mode ψ̂(k,t) for small wave number k=∣k∣. Upper bounds for ⟨ψ2⟩ and ∣ψ̂(k,t)∣2 are derived. The growth of ⟨ψ2⟩ is at most quadratic in time t and nearly quadratic in time for surface quasigeostrophic and Euler flows, respectively. At the modal level, it is found that ∣ψ̂(k,t)∣2≤ck2t2 and ∣ψ̂(k,t)∣2≤c′t2, where c and c′ are constant, for the surface quasigeostrophic and Euler cases, respectively. These bounds imply a steep energy spectrum at small k respectively, k5 and k3. The latter is consistent with previous statistical predictions and numerical results.
Nonresonant carrier tunneling in arrays of silicon nanocrystals
Authors: Lockwood R. , Hryciw A. , Meldrum A.
Published: January 2007

Silicon nanocrystals are of interest in the nascent field of silicon microphotonics, with potential applications as waveguide amplifiers, light-emitting diodes, and silicon-based lasers. Comparing computational simulations and experiment, it is shown that nonresonant carrier tunneling in ensembles of silicon nanocrystals is a controlling factor in the luminescence. In thin film silicon nanocrystal composites, only the larger particles can be luminescent as a result of rapid carrier tunneling, suggesting that these applications may only be achieved for well-isolated nanocrystals or for arrays with a narrow distribution of sizes.
Efficient solid-state host-guest light-emitting electrochemical cells based on cationic transition metal complexes
Authors: Su Hai-Ching , Wu Chung-Chih , Fang Fu-Chuan , Wong Ken-Tsung
Published: January 2007

The authors demonstrate highly efficient solid-state light-emitting electrochemical cells (LECs) consisting of green-emitting [Ir(dFppy)2(SB)]+(PF6−) as the host and orange-emitting [Ir(ppy)2(SB)]+(PF6−) as the guest [where dFppy is 2-(2,4-difluorophenyl)pyridine, SB is 4,5-diaza-9,9′-spirobifluorene, and ppy is 2-phenylpyridine]. Photophysical studies show that with the optimized host-guest compositions, the emission is mainly from the guest and photoluminescence quantum yields are largely enhanced over those of pure host and guest films due to suppressed intermolecular interactions. Correspondingly, LECs based on such host-guest cationic complex systems show substantially enhanced quantum efficiencies (power efficiencies) of up to 10.4% (36.8lm∕W), representing a 1.5 times enhancement compared to those of pure host and guest devices. Such results indicate that the host-guest system is essential and useful for achieving highly efficient solid-state LECs.
Optical measurements of the thermal properties of nanofluids
Authors: Rusconi Roberto , Rodari Erica , Piazza Roberto
Published: January 2007

The authors show that the thermal conductivity and diffusivity of colloidal particle dispersions can be rapidly obtained with high accuracy and reproducibility by exploiting a noninvasive, all-optical thermal lensing method. Applications of this technique to model suspensions of spherical monodisperse particles suggest that classical models for the effective properties of composite media hold up to rather high volume fractions, while no “anomalous” thermal conductivity effects are found.
CO2Enhancement of Aerobic and Hypoxic C2H4 Production in the Tissues of Cocklebur Seeds at Different Dormant States
Authors: Esashi Y , Saijoh Y , Saitoh H , Ishida S , Satoh S
Published: December 2006

CO2 stimulated C2H4 production in the axial and cotyledonary tissues of cocklebur (Xanthium pensylvanicum Wallr.) seeds regardless of their dormant states. Axial tissues were more responsive to CO2 than cotyledonary ones, and the tissues of upper seeds were more responsive than those of lower ones. Responsiveness of upper seed tissues to CO2 increased in the following order: primarily dormant (PD), non-dormant (ND) and secondarily dormant (SD) and also with increasing the period of presoaking. The CO2 stimulation of C2H4 production occurred not only in air but also under hypoxic conditions. The pronounced C2H4 production at hypoxia in the axes of PD seeds, as compared with those of ND ones, was a result of more active CO2 evolution in PD axes than in ND ones. A lag period of 2-3 h was required for the CO2 enhancement of C2H4 production to occur, and the CO2-enhanced C2H4 production was completely inhibited by aminoethoxyvinylglycine. It was thus suggested that CO2 may promote C2H4 production by stimulating the biogenesis of 1-aminocyclopropane-1-carboxylic acid.
Also, the seed-coat of cocklebur seeds produced C2H4 and its C2H4 production was enhanced by CO2. It thus became obvious that the enhancement of C2H4 production by CO2 is independent of the growth stimulation of seed tissues by CO2, since the seed-coat itself has no growth potential.
Translocation and Distribution of 14C-labelled Assimilate associated with Growth of Jute (Corchorus olitorius L.)
Authors: Palit P
Published: December 2006

Assimilate translocation from different source leaves and the partitioning of whole plant photosynthates
at different growth stages of jute (Corchorus olitorius L.) was studied in the field using I4CO,.
The I4C assimilates from the terminal source leaves were translocated to the apical bud and to other
developing leaves at the top of the plant while the middle leaves supplied only the adjacent stem sections.
The lower leaves exported to the basal internodes and the roots. Removal of all the leaves excepting
the six terminal ones reduced but did not stop apical growth, but checked the growth in stem diameter
completely. The results are discussed in relation to what is known of the general pattern of jute growth
by the apical meristem and the cambium.
The I4C assimilated by the whole plant was translocated to and accumulated in the parts according
to their mode of development. The carbon assimilated at 40 days from sowing was distributed mainly
to the leaves, but at 62 days it was distributed almost equally to the leaves, wood and bark. The carbon
assimilated at 105 days accumulated to the greatest extent in the wood. Distribution of assimilate to
the bark, which produces the yield of jute, was best during the early stages, increased to a maximum
during the second month but declined again at the later stages.
Stem cells and lineage development in the mammalian blastocyst
Authors: Rossant Janet
Published: December 2006

The mammalian blastocyst is the source of the most pluripotent stem cells known: embryonic stem (ES) cells. However, ES cells are not totipotent; in mouse chimeras, they do not contribute to extra-embryonic cell types of the trophectoderm (TE) and primitive endoderm (PrE) lineages. Understanding the genetic pathways that control pluripotency v. extra-embryonic lineage restriction is key to understanding not only normal embryonic development, but also how to reprogramme adult cells to pluripotency. The trophectoderm and primitive endoderm lineages also provide the first signals that drive patterned differentiation of the pluripotent epiblast cells of the embryo. My laboratory has produced permanent mouse cell lines from both the TE and the PrE, termed trophoblast stem (TS) and eXtra-embryonic ENdoderm (XEN) cells. We have used these cells to explore the genetic and molecular hierarchy of lineage restriction and identify the key factors that distinguish the ES cell v. the TS or XEN cell fate. The major molecular pathways of lineage commitment defined in mouse embryos and stem cells are probably conserved across mammalian species, but more comparative studies of lineage development in embryos of non-rodent mammals will likely yield interesting differences in terms of timing and details.
Maternally derived transcripts: identification and characterisation during oocyte maturation and early cleavage
Authors: Cui Xiang-Shun , Kim Nam-Hyung
Published: December 2006

The identification and characterisation of differentially regulated genes in oocytes and early embryos are required to understand the mechanisms involved in maturation, fertilisation, early cleavage and even long-term development. Several methods, including reverse transcription–polymerase chain reaction-based suppression subtractive hybridisation, differential display and cDNA microarray, have been applied to identify maternally derived genes in mammalian oocytes. However, conventional gene-knockout experiments to determine specific gene functions are labour intensive and inefficient. Recent developments include the use of RNA interference techniques to establish specific gene functions in mammalian oocytes and early embryos. Regulation of the poly(A) tail length is a major factor in controlling the activities of maternal transcripts in mammals. Further studies are required to clarify the mechanisms by which expression levels of maternally derived transcripts are regulated. In the present review, we focus on the identification and functions of the differentially expressed transcripts during oocyte maturation, fertilisation and early cleavage.
Embryo culture and long-term consequences
Authors: Thompson Jeremy G. , Mitchell Megan , Kind Karen L.
Published: December 2006

The development of pre-elongation (ruminants) and preimplantation (e.g. mouse and humans) embryos ex vivo has evolved over the past four decades into a reliable technology that is used as a research tool in developmental biology, as well as other embryo technologies, for application in infertility treatment, species conservation and selective breeding. It is clear from a variety of embryo culture studies that adaptive responses by embryos during culture can lead to significant alterations in subsequent developmental profiles, the mechanisms of which are not entirely clear but are unlikely to be limited to a single mechanism because this does not account for the variability seen in responses and the emerging list of specific cellular stressors that cause long-term deviations in fetal development. Epigenetic mechanisms, especially deviation of methylation patterns, and adaptation via causal pathways linking gene expression signalling with critical developmental time points, especially of placental development, are two candidates. Observational studies on post-transfer consequences must now be designed so that specific candidate pathways are followed to elucidate their role in perturbed development following transfer.
Long-term effects of nutritional programming of the embryo and fetus: mechanisms and critical windows
Authors: Symonds Michael E. , Stephenson Terence , Gardner David S. , Budge Helen
Published: December 2006

The maternal nutritional and metabolic environment is critical in determining not only reproduction, but also long-term health and viability. In the present review, the effects of maternal nutritional manipulation at defined stages of gestation coinciding with embryogenesis, maximal placental or fetal growth will be discussed. Long-term outcomes from these three developmental windows appear to be very different, with brain and cardiovascular function being most sensitive to influences in the embryonic period, the kidney during placental development and adipose tissue in the fetal phase. In view of the similarities in fetal development, number and maturity at birth, there are close similarities in these outcomes between findings from epidemiological studies in historical human cohorts and nutritional manipulation of large animals, such as sheep. One key nutrient that may modulate the long-term metabolic effects is the supply of glucose from the mother to the fetus, because this is sensitive to both global changes in food intake, maternal glucocorticoid status and an increase in the carbohydrate content of the diet. The extent to which these dietary-induced changes may reflect epigenetic changes remains to be established, especially when considering the very artificial diets used to induce these types of effects. In summary, the maintenance of a balanced and appropriate supply of glucose from the mother to the fetus may be pivotal in ensuring optimal embryonic, placental and fetal growth. Increased or decreased maternal plasma glucose alone, or in conjunction with other macro- or micronutrients, may result in offspring at increased risk of adult diseases.
10 EFFECTS OF INSEMINATION TIME, BREED, AND INSEMINATOR ON FERTILITY OF EWES INTRAUTERINALLY INSEMINATED WITH FROZEN - THAWED SEMEN IMPORTED FROM NEW ZEALAND
Authors: Fukui Y. , Kohno H. , Togari T. , Matsuoka T. , Imai H.
Published: December 2006

Artificial insemination, especially with the use of frozen semen, is one of the important tools for embryo transfer program in sheep. The present study investigated the effects of insemination times, breeds, and two inseminators on the fertility of ewes intrauterinally inseminated with frozen–thawed ram semen imported from New Zealand. At 8 sheep farms located in Hokkaido, Japan, during the breeding season (October to December) in 2005, a total of 64 mature (1- to 6-year old) Suffolk (32 heads) and Polled Dorset (32 heads) ewes were used. The ewes were treated with controlled intravaginal drug release (CIDR containing 0.3 g progesterone; Pharmacia & Upjohn, Ltd., Auckland, New Zealand) for 12 days and an injection of 500 IU equine chorionic gonadotropin one day before CIDR removal. The fixed-time intrauterine inseminations (early: 43–46 h; late: 47–50 h) after CIDR removal were performed using the frozen–thawed semen from a Suffolk and Polled Dorset ram by two inseminators. The effects of breeds (Suffolk and Polled Dorset), fixed-time insemination times (early and late phases), and two inseminators on pregnancy (number of pregnant ewes/number of ewes inseminated, 60 days after insemination) and lambing (number of lambed ewes/number of ewes inseminated) rates were analyzed by chi-square test. The prolificacy was compared by Student's t-test, and differences were also analyzed by Tukey's omega procedure. The effect of the different farms on fertility was not examined due to the small numbers of ewes per farm. Pregnancy (60.0 and 72.4%, respectively) and lambing (60.0 and 71.4%, respectively) rates were not significantly different between Suffolk and Polled Dorset ewes. The inseminators also did not affect pregnancy (62.6 and 68.8%) and lambing (62.6 and 67.7%) rates. For the insemination times, the lambing rate tended to be higher (P ≤ 0.10) in the early insemination than in the late insemination (76.7% and 53.6%, respectively). The present results show acceptable fertility in ewes inseminated with Suffolk and Polled Dorset frozen semen imported from New Zealand. The early intrauterine insemination (43–46 h after CIDR removal) tended to result in higher fertility than the late insemination (47–50 h after CIDR removal). From 38 lambed ewes, 60 newborn lambs were produced, and this has provided new blood lines of Suffolk and Polled Dorset sheep in Japan.
102 RABBIT CLONING: HISTONE ACETYLATION STATUS OF DONOR CELLS AND CLONED EMBRYOS
Authors: Zakhartchenko V. , Yang F. , Hao R. , Wolf E.
Published: December 2006

Epigenetic status of the genome of a donor nucleus is likely to be associated with the developmental potential of cloned embryos produced by somatic cell nuclear transfer (SCNT). Prevention of epigenetic errors by manipulation of the epigenetic status of donor cells is expected to result in improvement of cloning efficiency. In this study, we transferred cultured rabbit cumulus cells (RCC) and fetal fibroblasts (RFF) from genetically marked rabbits (Ali/Bas) into metaphase II (MII) oocytes and analyzed the levels of histone H3K9 acetylation in donor cells and cloned embryos. We also assessed the correlation between the histone acetylation status of donor cells and cloned embryos and their developmental potential. To test whether alteration of the histone acetylation status affects development of cloned embryos, we treated donor cells with sodium butyrate (NaBu), a histone deacetylase inhibitor. Further, we tried to improve cloning efficiency by chimeric complementation of cloned embryos with one or two blastomeres from in vitro-fertilized or parthenogenetic embryos. Histone acetylation in donor cells and cloned embryos was detected by anti-acH3K9 antibody using Western immunoblot analysis or immunochemistry, respectively. Data were analyzed by chi-square (developmental rates) or Student-Newman-Keuls (histone acetylation) test. The levels of acetylated histone H3K9 were higher in RCCs than in RFFs (P < 0.05). Although the type of donor cells did not affect development to blastocyst, after transfer into recipients, RCC-cloned embryos induced a higher initial pregnancy rate as compared to RFF-cloned embryos (40% vs. 20%; P < 0.05). However, almost all pregnancies with either type of cloned embryos were lost by the middle of gestation and only one fully developed; a live RCC-derived rabbit was obtained. Treatment of RFFs with NaBu significantly (P < 0.05) increased the level of histone H3K9/14 acetylation and the proportion of nuclear transfer embryos developing to blastocyst (49% vs. 33% with non-treated RFF; P < 0.05). The distribution of signals for acH3K9 in either group of cloned embryos did not resemble that in in vivo-fertilized embryos, suggesting that reprogramming of this epigenetic mark is aberrant in cloned rabbit embryos and cannot be corrected by treatment of donor cells with NaBu. Aggregation of embryos cloned from NaBu-treated RFFs with blastomeres from in vivo-derived embryos improved development to blastocyst, but no cloned offspring were obtained. Two live cloned rabbits were produced from this donor cell type only after aggregation of cloned embryos with a parthenogenetic blastomere. Our study demonstrates that the levels of histone acetylation in donor cells and cloned embryos correlate with their developmental potential and can be a useful epigenetic mark to predict efficiency of SCNT rabbits.
This work was supported by the Bayerische Forschungsstiftung and by Therapeutic Human Polyclonals, Inc.