bluuebunny/crossref_metadata_2025 huggingface dataset:
Carrier‐mediated stabilization of ferromagnetism in semiconductors: holes and electrons
Authors: Dalpian G. M. , Wei Su‐Huai
Published: July 2006

Band structure models are proposed to help understand carrier‐induced ferromagnetism in diluted magnetic semiconductors. We describe both hole‐ and electron‐mediated ferromagnetism. For hole‐mediated ferromagnetism, we show that there are two distinct mechanisms related to the stabilization of ferromagnetism. The difference between them is related to the position of the impurity d levels with respect to the valence band edge. If the impurity states are in the band gap, ferromagnetism can be explained by double exchange, which is related to the direct coupling between the impurity levels, whereas if the filled impurity states are below the VBM, ferromagnetism can be explained by the Zener model, which is related to the coupling between the impurity d levels and the host valence p states. In both cases, it is necessary to have holes, either free or localized, to stabilize the ferromagnetism. Our model successfully explains the ground state magnetic configuration of CdMnTe, GaMnAs, ZnMnO, and GaMnN. An extension of our model can also successfully explain the intriguing behavior of GaMnN. We show that at low Mn concentration, its ground state is FM, although AFM can be stabilized by increasing the Mn concentration, applying pressure, or by compensating the holes. For electron‐mediated ferromagnetism, we point out that it is necessary first to increase the exchange splitting of the conduction band. This can be done by reducing the symmetry of the system, by quantum confinement, or by changing the magnetic impurities from transition metals to rare earths. Our results also clarify some issues related to experimental works, such as the negative exchange splitting of the conduction band in GaMnAs quantum wells and the stabilization of ferromagnetism in GaGdN. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic structure of Pd‐covered (10,0) carbon nanotube
Authors: Zhu Wenguang , Kaxiras Efthimios
Published: July 2006

We report a first‐principles study on the electronic structure of a semiconducting (10,0) single‐wall carbon nanotube fully covered by Pd electrode, which closely resembles experimental setups. The equilibrium structure, charge transfer effects, electrostatic potentials, and the density of states are studied in detail, in order to establish whether a barrier exists or not between the natotube and the metal contact. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison between color Doppler cineloop‐ and conventional spectral Doppler‐derived maximum velocity and flow in the umbilical vein
Authors: Gerada M. , Struijk P. C. , Stewart P. A. , Guerriero S. , Melis G. B. , Wladimiroff J. W.
Published: July 2006

Objective

To compare the umbilical venous flow velocity derived from color Doppler cineloop recordings with that derived from conventional spectral Doppler in normal pregnancies.

Method

In 18 uncomplicated pregnancies between 19 and 39 weeks' gestation, color Doppler was used to find the maximum velocity in the cross‐sectional vessel area of a free‐floating loop of the umbilical vein. The maximum velocity was determined using the software tool HDI_Lab (Philips Medical Systems) after tracing the vessel area of interest. Conventional spectral Doppler was then used to determine the maximum velocity with the High‐Q machine option. The cross‐sectional area of the umbilical vein was determined using B‐mode imaging and was subsequently used to determine the umbilical volume flow from both Doppler methods. Assuming a parabolic flow profile in the umbilical vein, the mean velocity is equal to half the maximum velocity. The fetal weight was estimated from fetal biometry using the four‐parameter Hadlock formula.

Results

Maximum velocity was significantly (P = 0.003) higher with color Doppler cineloop (14.3 ± 2.5 cm/s) compared with spectral Doppler (12.7 ± 3.2 cm/s). Therefore, using the same cross‐sectional area for both methods, the umbilical blood flow was significantly higher (P = 0.001) with color Doppler cineloop (127.9 ± 59.0 mL/min) than it was with spectral Doppler (112.8 ± 54.1 mL/min). The umbilical blood flow expressed as volume flow per kg fetal weight was significantly (P = 0.01) higher with color Doppler cineloop (126.0 ± 57.0 mL/min/kg) than it was with spectral Doppler (115.0 ± 53.0 mL/min/kg).

Conclusions

Umbilical venous flow velocity derived from color Doppler cineloops is approximately 10% higher than that derived from spectral Doppler‐derived velocity. The reduced angle dependence of the color Doppler cineloop technique and the large sampling area of the cross‐sectional vessel should allow better determination of the correct maximum velocity in the umbilical vein. Copyright © 2006 ISUOG. Published by John Wiley & Sons, Ltd.
Performance analysis of the forward link cdma2000 1xEV‐DO evolution for multirate services in cellular wireless system
Authors: Matalgah Mustafa M. , Radaydeh Redha M. , Ismail Mahmoud H.
Published: July 2006

In this paper, we propose a combined analytical and simulation framework for performance evaluation of the forward link in the cdma2000 evolution for data only (1xEV‐DO) cellular systems with throughput and spectral efficiency being used as performance metrics. A closed form expression for the aggregate average throughput is derived in terms of system‐dependent parameters and a discrete random process that reflects the stochastic behavior of the transmission channel. The random process is expressed in terms of the cumulative distribution function (CDF) of the users signal‐to‐interference‐plus‐noise ratio (SINR). Quantitative results for throughput and spectral efficiency are presented for a variety of users distribution models, base station antenna types and frequency reuse factors for the cases of sectorized and non‐sectorized cells. Furthermore, we study the impact of the cell radius on the system performance. Copyright © 2006 John Wiley & Sons, Ltd.
Performance of coded DS‐CDMA system using reduced rank MMSE receiver in Rayleigh fading channels
Authors: Almutairi Ali F. , GabAllah Mohammed M.
Published: July 2006

This paper examines the performance of a reduced rank minimum mean square error (MMSE) receiver‐based direct sequence code division multiple access (DS‐CDMA) system. For such system, when a large processing gain is employed, substantial time is consumed in computing the filter tap weights. Many schemes for reducing the complexity of the MMSE have been proposed in recent years. In this paper, computational complexity reduction of the MMSE receiver is achieved by using the K‐mean classification algorithm. The performance of the uncoded and coded systems are investigated for the full rank MMSE receiver and reduced rank MMSE receiver and results are compared in terms of bit error rate at different loading levels in both AWGN and fading channels. A system with the matched filter (MF) receiver is also presented for the purpose of comparison and an analytical pair‐wise error bound for the coded system is derived. In the adaptive implementation of the receivers, results show that good performance is achieved for the reduced rank receiver when compared to the full rank receiver in both coded and uncoded systems, while in the optimum implementation of the tap weights, the reduced dimension receiver performance experiences degradation when compared to the full rank scheme. Over the band‐limited channels considered, results for the reduced rank receiver also reiterate the fact that higher code rates tend to yield lower BER than that of low rate codes. Copyright © 2006 John Wiley & Sons, Ltd.
Ser/Thr‐rich domains are associated with genetic variation and morphogenesis inSaccharomyces cerevisiae
Authors: Bowen Suzanne , Wheals Alan E.
Published: July 2006

Proteins containing regions of amino acid bias are often found in eukaryotes and are associated with particular functional groups. We have carried out a genomic analysis of yeast proteins containing regions with a significant bias of Ser and Thr residues. Our findings reveal that a high number are cell surface proteins or regulatory proteins involved in many aspects of cell differentiation. Furthermore, inSaccharomyces‐related species, a highly significant correlation exists between the frequency of Ser‐rich regions and DNA repeats, indicating that their generation may rely on similar factors. Cluster analysis shows that Ser/Thr‐rich regions, located within the tandem repeats of cell surface proteins, are encoded to an increased frequency by UCU (Ser) and ACU/ACC (Thr), implying that mutational events that generate iterations could involve these codons. Replication slippage is proposed to be a contributing factor, as mounting evidence suggests that repeat generation in cell surface proteins can occur independently of meiosis. To reinforce this argument, we have discovered a premeiotic association between Mre11p, a nuclease involved in DNA repair, and ORFs encoding Ser/Thr‐rich regions. Several macromolecules involved in the glycosylation and phosphorylation of proteins require Ser and Thr residues as binding sites. Ser/Thr‐rich regions, through polymorphisms, are associated with the evolution of functional sites, particularly in providing motifs for glycosylation and phosphorylation. These results point to a Ser/Thr‐biased somatic mutation mechanism that contributes to rapid evolution in yeast. Copyright © 2006 John Wiley & Sons, Ltd.
Removal of Cancellous Bone Graft through the Base of the Excised Radial Styloid Process
Authors: VOCHE P. , MERLE M.
Published: July 2006

In performing STT arthrodesis, the excision of the tip of the radial styloid avoids further radial styloid impingement. Cancellous bone graft can be obtained through the base of the excised radial styloid, using a trephine or a curette. The amount of bone removed is sufficient for intercarpal arthrodesis.
The Reverse Radial Forearm Flap in the Severely Injured Hand: An Anatomical and Clinical Study
Authors: CAVANAGH S. , PHO R. W. H.
Published: July 2006

An anatomical study in 25 cadaveric upper limbs quantified the communications between the radial and ulnar arteries immediately proximal to the carpus. These studies suggest that the reverse radial forearm flap can safely be used in severe hand trauma where reliable pre-operative assessment of the palmar collateral circulation is not possible. It is recommended that the pedicle is pivoted 4 cm from the styloid process at which point there is a 96% probability of leaving the superficial palmar branch and one other communication intact and a 77% probability of leaving two other communications intact. Two clinical cases are outlined for illustration.
Subungual Exostosis in the Hand
Authors: CARROLL R E. , CHANCE J. T. , INAN Y.
Published: July 2006

Although it is thought to be a relatively common tumour, only 34 positively identified cases of subungual exostosis in the hand have been found in the literature to date. 16 further cases are reported, making this the largest published series. Seven cases presented with an incorrect diagnosis. An X-ray easily differentiates the tumour from an osteochondroma of the distal phalanx, a spike of bone from a crush injury, or a response to a penetrating injury called a turret exostosis. Removal of the deformed nail and excision of the mass from the distal phalanx produces a useful ringer without pain, tender scar, or resultant nail deformity. No case of malignancy has ever been reported.
Otogenic brain abscess: management by otologist
Authors: Syal R , Singh H , Duggal K K
Published: July 2006

Introduction: Fifty per cent of brain abscesses in adults and 25 per cent of those in children are otogenic in origin. The current neurosurgical options are to drain the abscess repeatedly through burr holes or to excise it completely with the capsule. We successfully managed 10 cases of brain abscess by draining through the transmastoid route. The technique and its advantages are discussed.

Material and methods: The patients underwent surgery at two different institutions. Computed tomography scanning and magnetic resonance imaging were performed, along with diffusion-weighted imaging and in vivo proton magnetic resonance spectroscopy. The abscesses were drained via a transmastoid route.

Results: In eight cases, ear disease and brain abscess were treated in a single-stage procedure. In the remaining two cases, residual brain abscess was excised subsequently by our neurosurgical colleagues.

Conclusions: Transmastoid drainage of pus can successfully treat mastoid disease and brain abscess in a single surgical intervention. Residual abscess can be subsequently excised, with relatively reduced morbidity. Repeated needling is also avoided with this approach. Diffusion-weighted imaging and proton magnetic resonance spectroscopy are helpful.
Political Office and Household Wealth: Rural China in the Deng Era
Authors: Walder Andrew G. , Zhao Litao
Published: July 2006

Evidence from sample surveys and local field studies have long supported opposed arguments about the impact of market reform on the value of political office in the rural economy. This article reviews the evidence, describes a gradual convergence in findings, and identifies unresolved questions about qualitatively different local paths of development. Examining previously unexploited data from a nationally representative 1996 survey, a resolution of the remaining issues becomes evident. The value of political office initially is very modest, as the first private entrepreneurs reaped large incomes. However, subsequent economic development led to rapid increases in the earning power of cadres and their kin, and by the end of the Deng era the returns to political office were roughly equal to those of private entrepreneurs. The political advantages were not limited to regions that industrialized rapidly under collective ownership: they were large even in regions where the private economy was most extensive. However, despite evidence of large and enduring political advantages, those who reaped wealth from political position were only a small fraction of the newly rich, the vast majority of whom achieved wealth without current or past office-holding or kinship ties to cadres.
The Political Economy of Township Government Debt, Township Enterprises and Rural Financial Institutions in China
Authors: Ong Lynette
Published: July 2006

This article sheds light on the ways in which township governments mobilized resources from local financial institutions, and how failure to repay many of these loans gave rise to sizeable local government debt. Mobilization of resources was done through loans to collective enterprises whose de facto owners were township authorities. Though the enterprises were nominal borrowers, loan transactions would not have occurred without guarantees by township governments. Another way of financial resource mobilization was by establishing local informal financial organizations that were subject to less strict regulations, and over which township authorities could exercise control. Further, because the enterprises' profits and taxes ultimately went to township authorities, and the enterprises also contributed towards provision of public goods that were the authorities' obligation, enterprise financing became a roundabout way in which township authorities sought financial assistance for their fiscal needs.
Regulated expression of TAF1 in 1-cell mouse embryos
Authors: Wang Kai , Sun Feng , Sheng Hui Z.
Published: July 2006

TATA binding protein (TBP) associated factor 1 (TAF1) is a member of the general transcription machinery. Interference in the function of TAF1 causes a broad transcriptional defect in early development. To explore possible roles of TAF1 in embryonic transcriptional silence and zygotic genome activation, we examined the expression of TAF1 in 1-cell mouse embryos. Using an immunofluorescence assay, TAF1 was not detected in embryos in the first few hours after fertilization. TAF1 appeared in pronuclei 6 h post-fertilization and reached a relatively high level before zygotic genome activation. These data show that besides TBP, another critical member of the general transcription machinery such as TAF1 is also absent or at an extremely low level at the outset of development. Combined deficiency in critical members of the general transcription machinery may account for embryonic transcriptional silence.
Structural and ultrastructural analysis of embryonic development ofProchilodus lineatus(Valenciennes, 1836) (Characiforme; Prochilodontidae)
Authors: Ninhaus-Silveira Alexandre , Foresti Fausto , de Azevedo Alexandre
Published: July 2006

This survey was performed to characterize the embryogenesis ofProchilodus lineatus. Seven stages of embryo development were identified – zygote, cleavage, blastula, gastrula, segmentation, larval and hatching – after a period of incubation of 22 h (24 °C) or 14 h (28 °C). The following cleavage pattern was identified: the first plane was vertical (2 blastomeres); the second was vertical and perpendicular to the first (4 blastomeres); the third was vertical and parallel to the first (4 × 2); the fourth cleavage was vertical and parallel to the second (4 × 4); the fifth was vertical and parallel to the first (4 × 8); and the sixth cleavage was horizontal (64 blastomeres). At the blastula stage (3.0–4.0 h (24 °C); 1.66–2.0 h (28 °C)) irregular spaces were detected and periblast structuring was initiated. At the gastrula stage (4.0–8.0 h (24 °C); 3.0–6.0 h (28 °C)) the epiboly, convergence and cell movements, as well as the formation of embryonic layers, had begun. The segmentation stage (10.0–15.0 h (24 °C); 7.0–10.0 h (28 °C)) was characterized by a rudimentary formation of organs and systems (somites, optic vesicle and intestinal delimitation). The embryo at the larval stage (16.0–21.0 h (24 °C); 11.0–13.0 h (28 °C)) showed a free tail, more than 25 somites, an optic vesicle and a ready-to-hatch larval shape. The blastomeres at cleavage stage had disorganized nuclei indicating high mitotic activity. At gastrula, the blastomeres and the periblast had euchromatic nuclei and a large number of mitochondria and vesicles. The yolk was organized into globose sacs, which were dispersed into small pieces prior to absorption.
Structures related to the germ plasm in mouse
Authors: Reunov Arkadiy
Published: July 2006

This report presents data from ultrastructural and morphometric studies on the germinal-body-like structures, nuage, nuage–mitochondrial clusters and chromatoid bodies in 4.5-day embryo cells and spermatogenic cells of the laboratory mouseMus musculus. In the 4.5-day embryo cells the germinal-body-like structures that, according to previous data, arise by condensation of mitochondria in Graafian oocytes, were found not to undergo any ultrastructural alterations. In spermatogonia the germinal-body-like structures presumably were transformed into nuage that functioned as ‘intermitochondrial cement’ binding the mitochondrial clusters. In primary spermatocytes mitochondria aggregated by nuage were found with large vacuoles containing membraneous conglomerates that were obviously excreted by organelles into the cytoplasm. The chromatoid bodies that arose in spermatocytes and finally disintegrated in the posterior part of late spermatids seemed not to be implicated in the pathway of the germinal-body-like structure. The dispersion of chromatoid bodies was noted to be accompanied by excretion of membraneous conglomerates by late spermatid mitochondria. The spermatozoa were not found to contain either the germinal-body-like structures or any other germ-plasm-related structures.
Segmentation and alignment of parallel text for statistical machine translation
Authors: DENG YONGGANG , KUMAR SHANKAR , BYRNE WILLIAM
Published: July 2006

We address the problem of extracting bilingual chunk pairs from parallel text to create training sets for statistical machine translation. We formulate the problem in terms of a stochastic generative process over text translation pairs, and derive two different alignment procedures based on the underlying alignment model. The first procedure is a now-standard dynamic programming alignment model which we use to generate an initial coarse alignment of the parallel text. The second procedure is a divisive clustering parallel text alignment procedure which we use to refine the first-pass alignments. This latter procedure is novel in that it permits the segmentation of the parallel text into sub-sentence units which are allowed to be reordered to improve the chunk alignment. The quality of chunk pairs are measured by the performance of machine translation systems trained from them. We show practical benefits of divisive clustering as well as how system performance can be improved by exploiting portions of the parallel text that otherwise would have to be discarded. We also show that chunk alignment as a first step in word alignment can significantly reduce word alignment error rate.
The Saljūq Campaign against the Crimea and the Expansionist Policy of the Early Reign of ‘Alā’ al-Dīn Kayqubād
Authors: Peacock A. C. S.
Published: July 2006

The reign of Sultan ‘Alā’ al-Dīn Kayqubād (1219-1237) is depicted by both mediaeval and modern sources as the apogee of the Saljūq Sultanate of Rūm (Anatolia) (c. 1081–1308). The later court historian, Ibn Bībī, reflected subsequent generations' perception of ‘Alā’ al-Dīn when he recorded that “the earth has never borne a king the like of him, nor have the high heavens looked down on such a one”. Above all, his reign was remembered for the great military conquests that unified much of Anatolia under Saljūq rule. To the north, south and east neighbouring principalities, both Muslim and Christian, were either annexed outright or reduced to tributary status in a series of memorable campaigns.
The Establishment of Calcutta Botanic Garden: Plant Transfer, Science and the East India Company, 1786–1806
Authors: Thomas Adrian P.
Published: July 2006

Calcutta Botanic Garden occupies a prime riverside site three miles downstream from the centre of Calcutta. It is most famous as the home of the world's largest tree, a vast spreading banyan. Its grand avenues, named after its founders and the fathers of Indian botany, convey something of its former glory. In the nineteenth century it was the greatest of all the colonial botanic gardens and an important scientific institution; two of its superintendents were knighted and one went on to become Director of the Royal Botanic Gardens at Kew, the very centre of the imperial botanical network. The Garden is of considerable importance as it was one of the earliest institutions in India based on western science. This survey will look at the reasons for its foundation, and how it successfully established itself in its first twenty years.
Comparative study of microstructural evolution during melting and crystallization
Authors: Xiao Shifang , Hu Wangyu
Published: July 2006

Molecular dynamics simulations, with the interaction between atoms described by a modified analytic embedded atom method, have been performed to obtain the atomic-scale details of isothermal melting in nanocrystalline Ag and crystallization from supercooled liquid. The radial distribution function and common neighbor analysis provide a visible scenario of structural evolution in the process of phase transition. The results indicate that melting at a fixed temperature in nanocrystalline materials is a continuous process, which originates from the grain boundary network. With the melting developing, the characteristic bond pairs (555), (433), and (544), existing in liquid or liquidlike phase, increase approximately linearly till completely melted. The crystallization from supercooled liquid is characterized by three characteristic stages: nucleation, rapid growth of nucleus, and slow structural relaxation. The homogeneous nucleation occurs at a larger supercooling temperature, which has an important effect on the process of crystallization and the subsequent crystalline texture. The kinetics of transition from liquid to solid is well described by the Johnson-Mehl-Avrami equation.
Design of random copolymers with statistically controlled monomer sequence distributions via Monte Carlo simulations
Authors: Semler James J. , Genzer Jan
Published: July 2006

We use Monte Carlo simulations to model the formation of random copolymers with tunable monomer sequence distributions. Our scheme is based on the original idea proposed a few years ago by Khokhlov and Khalatur [Physica A 249, 253 (1998); Phys. Rev. Lett. 82, 3456 (1999)], who showed that the distribution of species B in A-B random copolymers can be regulated by (a) adjusting the coil size of a homopolymer A and (b) chemically modifying (“coloring”) monomers that reside at (or close to) the periphery of the coil with species B. In contrast to Khokhlov and Khalatur’s work, who modeled the polymer modification by performing the coloring instantaneously, we let the chemical coloring reaction progress over time using computer simulations. We show that similar to Khokhlov and Khalatur’s work, the blockiness (i.e., number of consecutive monomers) of the B species along the A-B copolymer increases with increasing degree of collapse of the parent homopolymer A. A simple analysis of the A-B monomer sequences in the copolymers reveals that monomer sequence distributions in homopolymers “colored” under collapsed conformations possess certain degrees of self-similarity, while there is no correlation found among the monomer sequence distributions formed by coloring homopolymers with expanded conformations.
Porous spherical burner for combustion experimentation
Authors: Yoo Sean W. , Zhu Delin , Law Chung K.
Published: July 2006

The design and fabrication of porous spherical burners for the production of spherically symmetric flows are reported. The burners are produced from sintering bronze powders in a spherical graphite mold, with the feed tube and the porous sphere produced in one piece. This offers the flexibility of installing tubes of varying sizes, yielding consistent results as compared to conventional methods in which the tubes are mechanically or chemically bonded to the bronze porous sphere. The versatility and quality of these burners are demonstrated through various images of spherical flames generated by issuing reactive gases through them in microbuoyancy conditions.
Photoelectron spectra of hydrated electron clusters: Fitting line shapes and grouping isomers
Authors: Coe James V. , Arnold Susan T. , Eaton Joseph G. , Lee Gang Ho , Bowen Kit H.
Published: July 2006

The photoelectron spectra of (H2O)n=2–69− and (D2O)n=2–23− are presented, and their spectral line shapes are analyzed in detail. This analysis revealed the presence of three different groupings of species, each of which are seen over the range, n=11–16. These three groups are designated as dipole boundlike states, seen from n=2–16, intermediate states, found from n=6–16, and bulk embryonts, starting at n=11 and continuing up through the largest sizes studied. Almost two decades ago [J. V. Coe et al., J. Chem. Phys. 92, 3980 (1990)], before the present comprehensive analysis, we concluded that the latter category of species were embryonic hydrated electrons with internalizing excess electrons (thus the term embryonts). Recent experiments with colder expansion (high stagnation chamber pressures) conditions by Neumark and coworkers [J. R. R. Verlet et al., Science 307, 93 (2005)] have also found three groups of isomers including the long-sought-after surface states of large water cluster anions. This work confirms that the species here designated as embryonts are in the process of internalizing the excess electron states as the cluster size increases (for n⩾11).
Two-dimensional nonclose-packed colloidal crystals formed by spincoating
Authors: Jiang Peng , Prasad Tushar , McFarland Michael J. , Colvin Vicki L.
Published: July 2006

We report a simple spin-coating technique for the production of monolayer nonclose-packed colloidal crystals. Dispersions of submicron silica spheres in triacrylate monomers are spincoated and polymerized to form two-dimensional colloidal crystal-polymer nanocomposites. By removing the polymer matrix, wafer-scale nonclose-packed colloidal crystals with high crystalline quality can be made. The technique is compatible with standard microfabrication and allows for the production of microstructures for potential devices. Normal-incidence reflectivity spectra in the visible and near-infrared regions show sharp peaks due to Bragg diffraction from the colloidal monolayers. The peak position matches with the theoretical prediction using scalar wave approximation.
70
-
mm
-long periodically poled Mg-doped stoichiometric LiNbO3 devices for nanosecond optical parametric generation
Authors: Maruyama Masayuki , Nakajima Hirochika , Kurimura Sunao , Yu Nan Ei , Kitamura Kenji
Published: July 2006

A low-threshold, nanosecond, optical parametric generator (OPG) was produced by using a 70-mm-long, periodically poled, Mg-doped, stoichiometric LiNbO3 (PPMgSLN). The periodically poled structure was obtained by applying an electric field of 1.8kV∕mm, which is lower than the coercive field of 3.9kV∕mm. The PPMgSLN OPG pumped with a 6ns, 6.8kHz, Nd:YAG microchip laser had a generation threshold of 12MW∕cm2 and a slope efficiency of 37% of signal at 1.61μm.
First direct observation of self-imaging effect in active multimode-interference semiconductor laser diodes
Authors: Shimizu Syogo , Razali Mohd Dannial Bin , Kasahara Kenichi , Hamamoto Kiichi , Ohya Masaki , Naniwae Koichi , De Merlier Jan , Shiba Kazuhiro , Sudo Shinya , Sasaki Tatsuya
Published: July 2006

We report the first direct observation of the self-imaging effect in active multimode-interference semiconductor laser diodes (MMI-SLDs). Interference patterns inside laser diode waveguides were obtained by using the electroluminescence (EL) method. To the best of our knowledge, this result is the first direct observation of the self-imaging effect in self-photon-emitting active waveguides such as laser diodes. The observed EL pattern confirms the adequateness of the design of the higher light output-aimed MMI-SLDs.
Atomic force microscopy based, multiphoton, photoelectron emission imaging
Authors: Spanakis E. , Chimmalgi A. , Stratakis E. , Grigoropoulos C. P. , Fotakis C. , Tzanetakis P.
Published: July 2006

Images of photoelectron emission from metallic surfaces were obtained with a modified atomic force microscope operating in air. Illumination of the samples was achieved in the near field of a metal-coated microcantilever tip, placed in the beam of a femtosecond pulsed laser that is incident at a grazing angle with respect to the sample surface. Photoelectron currents were measured through the tip with a prototype amplifier. The power law dependence of average photocurrent on light intensity is compatible with multiphoton photoelectric effect and the work function of the metal covering a particular area on the two-metal patterned samples used.
Search for ferromagnetism in conductive Nb:SrTiO3 with magnetic transition element (Cr, Co, Fe, Mn) dopants
Authors: Zhang S. X. , Ogale S. B. , Kundaliya Darshan C. , Fu L. F. , Browning N. D. , Dhar S. , Ramadan W. , Higgins J. S. , Greene R. L. , Venkatesan T.
Published: July 2006

Thin films of (0.5%, 1%) Nb:SrTiO3 dilutely doped with (2at.%) magnetic transition elements (Cr, Co, Fe, Mn) are examined for ferromagnetism. X-ray diffraction, Rutherford backscattering ion channeling, scanning transmission electron microscopy Z-contrast imaging, and electron energy loss spectroscopy techniques establish high crystalline quality of the films with no impurity phase(s) and highly uniform dopant distribution. Although the film conductivity improves dramatically by Nb doping, no ferromagnetism is found in any of our samples over the temperature range of 365 down to 5K. This is contrasted to the case of ferromagnetism reported in cobalt doped (La,Sr)TiO3.
Metal transport and loss in ultrathin hafnium aluminate films on silicon studied by low, medium, and high energy ion beam analyses
Authors: Miotti L. , Driemeier C. , Tatsch F. , Radtke C. , Baumvol I. J. R.
Published: July 2006

Metal transport and loss induced by thermal annealing in ultrathin HfAlxOy films deposited on Si by atomic layer deposition were investigated by ion beam analysis. It was observed that rapid thermal annealing at 1000°C induces decomposition of the aluminate films leading to Hf and Al losses mainly into the gas phase. It was possible to avoid this undesired decomposition effect by performing a postdeposition nitridation in NH3 at 850°C prior to the rapid thermal annealing step. The role of nitridation is discussed in terms of the profiles of incorporated N, before and after rapid thermal annealing, as determined by narrow resonant nuclear reaction profiling.
Inverted spin polarization of Heusler alloys for spintronic devices
Authors: Thomas Andy , Meyners Dirk , Ebke Daniel , Liu Ning-Ning , Sacher Marc D. , Schmalhorst Jan , Reiss Günter , Ebert Hubert , Hütten Andreas
Published: July 2006

A magnetic logic concept overcomes the major limitations of field programmable gate arrays while having a 50% smaller unit cell than conventional designs utilizing magnetic tunnel junctions with one Heusler alloy electrode. These show positive and negative tunneling magnetoresistance values at different bias voltages at room temperature which generally add an additional degree of freedom to all spintronic devices.
Single cell recordings with pairs of complementary transistors
Authors: Meyburg Sven , Wrobel Günter , Stockmann Regina , Moers Jürgen , Ingebrandt Sven , Offenhäusser Andreas
Published: July 2006

Floating gate field-effect transistors (FETs) for the detection of extracellular signals from electrogenic cells were fabricated in a complementary metal oxide semiconductor process. Additional passivation layers protected the transistor gates from the electrolyte solution. To compare the signals from n- and p-FETs, two electronically separated, but locally adjacent transistors were combined to one measuring unit. The paired sensing area of this unit had the dimension of a single cell. Simultaneous recordings with n- and p-channel floating gate FETs from a single cell exhibited comparable amplitudes and identical time courses. The experiments indicate that both types of FETs express similar sensitivities.
Hole emitter of photonic quantum ring
Authors: Kwon O’Dae , Kim M. J. , An S.-J. , Kim D. K. , Lee S. E. , Bae J. , Yoon J. H. , Park B. H. , Kim J. Y. , Ahn J.
Published: July 2006

We report on the observation of “hole” whispering gallery lasers from semiconductor microcavities with three dimensional optical confinement, with thresholds potentially reducible to micro- to nanoampere regimes according to a quadratic size-dependent reduction, consistent with a photonic quantum corral effect of naturally formed recombinant quantum rings. If the device size grows over a critical diameter, the quantum ring whispering gallery then begins to disappear. However, cooperative small hole laser arrays, exhibiting photonic crystal structure properties, avoid the criticality and open a possibility of constructing practical high-density electropumped emitter arrays.
Thermochemical reaction of ZrOx(Ny) interfaces on Ge and Si substrates
Authors: Cheng Chao-Ching , Chien Chao-Hsin , Lin Je-Hung , Chang Chun-Yen , Luo Guang-Li , Yang Chun-Hui , Hsu Shih-Lu
Published: July 2006

We have studied the thermochemical characteristics of ZrOx(Ny)∕Ge and Si interfaces by employing postdeposition annealing. We found that Ge oxide species severely desorbed from the inherent interfacial layer, which was speculated to retard the formation of Zr germanate during high-temperature processing. These unique features enable ZrOx(Ny)∕Ge gate stack to show a better equivalent-oxide-thickness scalability as compared to ZrOx(Ny)∕Si gate stack. However, the volatilization of GeOx-contained interfacial layer also caused the formation of small pits and/or holes in the overlying ZrOx(Ny) gate dielectrics, which was expected to cause deterioration in the electrical properties of fabricated high-k∕Ge devices.
Mobile atom traps using magnetic nanowires
Authors: Allwood D. A. , Schrefl T. , Hrkac G. , Hughes I. G. , Adams C. S.
Published: July 2006

By solving the Landau-Lifshitz-Gilbert equation using a finite element method we show that an atom trap can be produced above a ferromagnetic nanowire domain wall. Atoms experience trap frequencies of up to a few megahertz, and can be transported by applying a weak magnetic field along the wire. Lithographically defined nanowire patterns could allow quantum information processing by bringing domain walls in close proximity at certain places to allow trapped atom interactions and far apart at others to allow individual addressing.
Electrolytic fabrication of atomic clock cells
Authors: Gong F. , Jau Y.-Y. , Jensen K. , Happer W.
Published: July 2006

We describe an electrolytic method to release controlled amounts of free alkali metal into miniature cells in a silicon wafer with anodically bonded glass windows.
Noncontact tissue oxygenation measurement using near-infrared spectroscopy
Authors: Niwayama Masatsugu , Murata Hideaki , Shinohara Shigenobu
Published: July 2006

Here, we present a noncontact tissue oxygenation monitor that uses near-infrared spectroscopy (NIRS). We examined changes in sensitivity of tissue oxygenation measurement due to changes in the distance between the optical probe and the skin surface using a Monte Carlo simulation and in vivo tests. We also examined the effects of skin and fat layer thickness. Photon migration was analyzed in a model consisting of the skin, fat, and muscle layers. The relationship between measurement sensitivity and the probe-tissue distance was obtained from the results of the simulation and was used for correction of measurements. A noncontact tissue oximeter was used to perform the in vivo tests and measure oxygen consumption of the forearm muscle. The value of corrected oxygen consumption was 0.12±0.03ml∕(100gmin), which is consistent with previously reported values obtained using contact NIRS measurement and magnetic resonance spectroscopy. Quantitative measurement of oxygenation using noncontact NIRS is potentially useful for novel applications such as quantification of inflammation.
Increased Myosin Light Chain Kinase Expression in Hypertension: Regulation by Serum Response Factor via an Insertion Mutation in the Promoter
Authors: Han Yoo-Jeong , Hu Wen-Yang , Chernaya Olga , Antic Nenad , Gu Lianzhi , Gupta Mahesh , Piano Mariann , de Lanerolle Primal
Published: July 2006

Regulation of gene transcription in vascular smooth muscle cells (VSMCs) by serum response factor (SRF) plays a crucial role in vascular development and in the pathophysiology of vascular diseases. Nevertheless, the regulation of specific genes by SRF in vascular diseases is poorly understood. Therefore, we investigated the regulation of smooth muscle myosin light chain kinase (smMLCK) by using spontaneously hypertensive rats (SHR) as an experimental model. We found that smMLCK expression in blood vessels increases during the development of hypertension and is always greater in blood vessels from SHR compared with normotensive rats. Analysis of the DNA sequences of the promoters isolated from SHR and normotensive rats revealed that SHR contain a 12-base pair insertion adjacent to the CArG box. This insertion increases SRF binding to the CArG box and positively regulates SRF-dependent promoter activity. The increase in smMLCK expression was blocked by dominant-negative SRF, dominant-negative Ras, or antisense oligonucleotides to ERK. In vivo, inhibiting MEK decreased smMLCK expression and blood pressure in SHR partly by decreasing SRF binding to the smMLCK promoter. These data provide novel insight into the regulation of smMLCK expression at the molecular level and demonstrate the importance of SRF in regulating smMLCK promoter activity in SHR.
Microphthalmia-associated Transcription Factor Interactions with 14-3-3 Modulate Differentiation of Committed Myeloid Precursors
Authors: Bronisz Agnieszka , Sharma Sudarshana M. , Hu Rong , Godlewski Jakub , Tzivion Guri , Mansky Kim C. , Ostrowski Michael C.
Published: July 2006

The microphthalmia-associated transcription factor (MITF) is required for terminal osteoclast differentiation and is a target for signaling pathways engaged by colony stimulating factor (CSF)-1 and receptor-activator of nuclear factor-κB ligand (RANKL). Work presented here demonstrates that MITF can shuttle from cytoplasm to nucleus dependent upon RANKL/CSF-1 action. 14-3-3 was identified as a binding partner of MITF in osteoclast precursors, and overexpression of 14-3-3 in a transgenic model resulted in increased cytosolic localization of MITF and decreased expression of MITF target genes. MITF/14-3-3 interaction was phosphorylation dependent, and Ser173 residue, within the minimal interaction region of amino acid residues 141–191, was required. The Cdc25C-associated kinase (C-TAK)1 interacted with an overlapping region of MITF. C-TAK1 increased MITF/14-3-3 complex formation and thus promoted cytoplasmic localization of MITF. C-TAK1 interaction was disrupted by RANKL/CSF-1 treatment. The results indicate that 14-3-3 regulates MITF activity by promoting the cytosolic localization of MITF in the absence of signals required for osteoclast differentiation. This work identifies a mechanism that regulates MITF activity in monocytic precursors that are capable of undergoing different terminal differentiation programs, and it provides a mechanism that allows committed precursors to rapidly respond to signals in the bone microenvironment to promote specifically osteoclast differentiation.
A framework of integrating gene relations from heterogeneous data sources: an experiment onArabidopsis thaliana
Authors: Li Jiexun , Li Xin , Su Hua , Chen Hsinchun , Galbraith David W.
Published: July 2006

One of the most important goals of biological investigation is to uncover gene functional relations. In this study we propose a framework for extraction and integration of gene functional relations from diverse biological data sources, including gene expression data, biological literature and genomic sequence information. We introduce a two-layered Bayesian network approach to integrate relations from multiple sources into a genome-wide functional network. An experimental study was conducted on a test-bed of Arabidopsis thaliana. Evaluation of the integrated network demonstrated that relation integration could improve the reliability of relations by combining evidence from different data sources. Domain expert judgments on the gene functional clusters in the network confirmed the validity of our approach for relation integration and network inference.

Contact:  jiexun@eller.arizona.edu
Sublocalization and Volumetric Growth Pattern of Intracanalicular Vestibular Schwannomas
Authors: Caye‐Thomasen Per , Hansen Søren , Dethloff Thomas , Stangerup Sven‐Eric , Thomsen Jens
Published: July 2006

Objective: None of several previous reports on the growth pattern of vestibular schwannomas (VS) have dealt with the sublocalization and volumetric growth pattern of intracanalicular tumors. This paper reports such data from 196 patients.

Study Design: All VS patients have been registered prospectively at one center in Denmark since 1975. Data on intracanalicular tumors were drawn from the database, yielding 196 patients with a diagnostic and at least one control magnetic resonance imaging scan. All images were retrieved and the tumor sublocalization, size, and growth rate determined.

Results: The majority (50%) of the tumors was located centrally in the internal auditory canal (IAC), whereas 31% were porus‐near and 19% fundus‐near. Of the 196 tumors, 88 (45%) displayed growth, 20 (10%) shrinkage, and 88 (45%) remained unchanged. Thirty‐eight (19%) tumors grew to extrameatal extension. Growth occurred only within 5 years after diagnosis. In the 88 growing tumors, the mean absolute growth rate was 111mm3/year and the relative rate 114%/volume/year. The occurrence of IAC expansion at diagnosis was higher for tumors displaying subsequent shrinkage. Growth occurrence and rate, IAC expansion, and progression to extrameatal extension were not related to tumor sublocalization.

Conclusion: Most intracanalicular VS are located centrally in a nonexpanded IAC at diagnosis. Growth occurs within 5 years after diagnosis in up to 45% of the tumors, although only 19% extend into the cerebellopontine angle. IAC expansion, growth occurrence, and rate are not related to tumor sublocalization. These findings justify primary observation of all purely intracanalicular tumors, unless realistic hearing preservation is intended.
Juvenile Spring Eruption: A Report of Two Cases
Authors: Dogru Salim , Gungor Atila , Cekin Engin , Cincik Hakan , Alga Omer Hilmi
Published: July 2006

Juvenile spring eruption is a photodermatosis characterized by the development of papules and vesicles on the light‐exposed helix of the ears after sun exposure, usually in the springtime. It mainly affects boys and young male adults, and has a tendency to occur in the form of small epidemics. We report an outbreak in a group of soldiers who were performing military exercises during cold and sunny weather during a midwinter season. The clinicopathologic features and laboratory test results are described in two of these cases.
Impact of Duty Hour Restrictions on Otolaryngology Training: Divergent Resident and Faculty Perspectives
Authors: Brunworth Joseph D. , Sindwani Raj
Published: July 2006

Objectives: In 2003, the Accreditation Council for Graduate Medical Education (ACGME) passed a controversial mandate limiting resident work hours. We sought to examine the impact of these restrictions on otolaryngology programs and to explore faculty and resident perspectives.

Methods: Faculty and residents of all 102 ACGME‐accredited otolaryngology residency programs were invited to participate in an anonymous online survey.

Results: The study population consisted of 460 respondents: 275 residents and 185 faculty (including 41 program directors) representing 57 otolaryngology programs. Sixty‐five percent of programs implemented at least one change specifically to comply with duty‐hour restrictions. Strategies included tracking work hours electronically (35.7%), utilization of “home call” (33.1%), and hiring additional healthcare professionals (23.1%). When asked if the restrictions have had a negative effect on patient care, 61% of respondents said no, but a surprising 33% said yes. Sixty‐nine percent of faculty felt that the restrictions have actually had a negative effect on resident training compared with only 31% of residents (P < .001). Thirty‐nine percent of participants felt resident workload was excessive before the restrictions. Opinions on whether duty‐hour limits had fostered improvements in resident education, research, or examination scores varied, but most agreed that resident mental health had improved (67%).

Conclusions: Otolaryngology programs have successfully restricted resident duty hours through significant infrastructural changes. Of concern, the majority of residents surveyed appeared to be in favor of the ACGME restrictions, whereas most program directors and faculty were opposed. Further studies are needed to establish whether limited work hours will enhance or hinder the residency training experience.