bluuebunny/crossref_metadata_2025 huggingface dataset:
Star Formation and Gas Dynamics in Galactic Disks: Physical Processes and Numerical Models
Authors: Ostriker Eve C.
Published: April 2011

Star formation depends on the available gaseous “fuel” as well as galactic environment, with higher specific star formation rates where gas is predominantly molecular and where stellar (and dark matter) densities are higher. The partition of gas into different thermal components must itself depend on the star formation rate, since a steady state distribution requires a balance between heating (largely from stellar UV for the atomic component) and cooling. In this presentation, I discuss a simple thermal and dynamical equilibrium model for the star formation rate in disk galaxies, where the basic inputs are the total surface density of gas and the volume density of stars and dark matter, averaged over ~kpc scales. Galactic environment is important because the vertical gravity of the stars and dark matter compress gas toward the midplane, helping to establish the pressure, and hence the cooling rate. In equilibrium, the star formation rate must evolve until the gas heating rate is high enough to balance this cooling rate and maintain the pressure imposed by the local gravitational field. In addition to discussing the formulation of this equilibrium model, I review the current status of numerical simulations of multiphase disks, focusing on measurements of quantities that characterize the mean properties of the diffuse ISM. Based on simulations, turbulence levels in the diffuse ISM appear relatively insensitive to local disk conditions and energetic driving rates, consistent with observations. It remains to be determined, both from observations and simulations, how mass exchange processes control the ratio of cold-to-warm gas in the atomic ISM.
Star Formation in Interacting Galaxies
Authors: Struck Curtis
Published: April 2011

This brief review emphasizes the wide range of environments where interaction induced star formation occurs. In these environments we can study the numerous elaborations of a few basic physical processes, including: gravitational instability, accretion and large-scale shocks.
Shock-induced star cluster formation in colliding galaxies
Authors: Saitoh Takayuki R. , Daisaka Hiroshi , Kokubo Eiichiro , Makino Junichiro , Okamoto Takashi , Tomisaka Kohji , Wada Keiichi , Yoshida Naoki
Published: April 2011

We studied the formation process of star clusters using high-resolutionN-body/smoothed particle hydrodynamics simulations of colliding galaxies. The total number of particles is 1.2×108for our high resolution run. The gravitational softening is 5 pc and we allow gas to cool down to ~10 K. During the first encounter of the collision, a giant filament consists of cold and dense gas found between the progenitors by shock compression. A vigorous starburst took place in the filament, resulting in the formation of star clusters. The mass of these star clusters ranges from 105−8M⊙. These star clusters formed hierarchically: at first small star clusters formed, and then they merged via gravity, resulting in larger star clusters.
Galaxy formation hydrodynamics: From cosmic flows to star-forming clouds
Authors: Bournaud Frédéric
Published: April 2011

Major progress has been made over the last few years in understanding hydrodynamical processes on cosmological scales, in particular how galaxies get their baryons. There is increasing recognition that a large part of the baryons accrete smoothly onto galaxies, and that internal evolution processes play a major role in shaping galaxies – mergers are not necessarily the dominant process. However, predictions from the various assembly mechanisms are still in large disagreement with the observed properties of galaxies in the nearby Universe. Small-scale processes have a major impact on the global evolution of galaxies over a Hubble time and the usual sub-grid models account for them in a far too uncertain way. Understanding when, where and at which rate galaxies formed their stars becomes crucial to understand the formation of galaxy populations. I discuss recent improvements and current limitations in “resolved” modeling of star formation, aiming at explicitly capturing star-forming instabilities, in cosmological and galaxy-sized simulations. Such models need to develop three-dimensional turbulence in the ISM, which requires parsec-scale resolution at redshift zero.
A Guide to Comparisons of Star Formation Simulations with Observations
Authors: Goodman Alyssa A.
Published: April 2011

We review an approach to observation-theory comparisons we call “Taste-Testing.” In this approach, synthetic observations are made of numerical simulations, and then both real and synthetic observations are “tasted” (compared) using a variety of statistical tests. We first lay out arguments for bringing theory to observational space rather than observations to theory space. Next, we explain that generating synthetic observations is only a step along the way to the quantitative, statistical, taste tests that offer the most insight. We offer a set of examples focused on polarimetry, scattering and emission by dust, and spectral-line mapping in star-forming regions. We conclude with a discussion of the connection between statistical tests used to date and the physics we seek to understand. In particular, we suggest that the “lognormal” nature of molecular clouds can be created by the interaction of many random processes, as can the lognormal nature of the IMF, so that the fact that both the “Clump Mass Function” (CMF) and IMF appear lognormal does not necessarily imply a direct relationship between them.
Legal authority and savagery in judicial rhetoric: sexual violence and the criminal courts
Authors: Gurnham David
Published: April 2011

This article explores narrative devices in legal rhetoric, and the use of these devices for asserting the authority to distinguish lawful from unlawful inflictions of bodily harm. The argument made here is that the moral language adopted by judges in criminal appeal judgments on risky sexual and/or violent consensual acts embraces a set of interconnecting narratives otherwise observed in literature, and relating to gender, sexuality and race. I try to show how the reading of these legal cases is enriched by identifying these narratives, locating them as rhetorical strategies and reflecting on their uses in judicial decision-making. In particular, I argue that in the case-law explored here, these interconnected narratives are deployed in order to assert law's dominance over an imagined ‘savage’ other. Through this ongoing repudiation of savagery the distinctions between normative and non-normative, violent and non-violent, lawful and unlawful are constructed.
Integrating human rights in emerging regulation of Corporate Social Responsibility: the EU case
Authors: Buhmann Karin
Published: April 2011

This article analyses the EU Commission's policy-based approach to regulating Corporate Social Responsibility (CSR) and the role of international human rights law as a normative source for the regulatory output in two initiatives launched in 2002 and 2006. The article argues as a starting point that the understanding of CSR as ‘beyond law’ tends to shroud the contributions that international human rights law and legal theory based regulatory technique lend to CSR normativity and regulation, not only outside the EU but also within. The EU experience shows that due to power relations and their impact on multi-stakeholder negotiations and their outcome, this potential does necessarily unfold. It also shows that the procedural design of reflexive multi-stakeholder regulatory processes is significant for bringing forth the normative contributions of international law to CSR in public–private regulation. Finally, the article suggests that within the public policy context in which EU CSR regulation is emerging, the normative role of international human rights law which the Commission suggests for CSR in Europe and the application of the reflexive regulatory technique contribute to a substantive as well as procedural juridification of CSR, especially in the formative stage of defining CSR normativity. The latter adds a significant new perspective to the understanding of CSR and its relation to law, although it need not conflict with the understanding of CSR being ‘voluntary’ in the sense of action beyond direct legal obligations.
Challenging homophobic bullying in schools: the politics of progress
Authors: Monk Daniel
Published: April 2011

In recent years homophobic bullying has received increased attention from NGOs, academics and government sources and concern about the issue crosses traditional moral and political divisions. This article examines this ‘progressive’ development and identifies the ‘conditions of possibility’ that have enabled the issue to become a harm that can be spoken of. In doing so it questions whether the readiness to speak about the issue represents the opposite to prohibitions on speech (such as the notorious Section 28) or whether it is based on more subtle forms of governance. It argues that homophobic bullying is heard through three key discourses (‘child abuse’, ‘the child victim’ and ‘the tragic gay’) and that, while enabling an acknowledgement of certain harms, they simultaneously silence other needs and experiences. It then moves to explore the aspirational and ‘liberatory’ political investments that underlie these seemingly ‘common-sense’ descriptive discourses and concludes with a critique of the quasi-criminal responses that the dominant political agenda of homophobic bullying gives rise to. The article draws on, and endeavours to develop a conversation between, critical engagements with the contemporary politics of both childhood and sexuality.
Habeas Corpus: from England to Empire
Authors: Lobban Michael
Published: April 2011

The ‘Great Writ’ of habeas corpus has long had an iconic status as the ‘writ of liberty’ which ensured that no person could be detained in prison without being put to trial by a jury of his peers. According to the traditional version, popularised by Whiggish constitutional writers from the late seventeenth century onwards, the English constitution as embodied in the common law had, since time immemorial, striven to protect the fundamental rights of Englishmen and women, which included the right to personal liberty. The common law had supplied the writ of habeas corpus, which secured the provision of Magna Carta, that no freeman be imprisoned save by the judgment of a jury of his peers. In the course of the seventeenth century, the Whig version ran, kings with an absolutist bent sought to undermine ancient liberties, by claiming prerogative powers to imprison without trial, and by appointing supine judges who would not protect people's liberties. It took the triumph of Parliament to restore and perfect them. For William Blackstone, one of the key statutes which secured ‘the complete restitution of English liberty’ was the Habeas Corpus Act of 1679, ‘that second magna carta’. As Blackstone put it:

‘Magna carta only, in general terms, declared, that no man shall be imprisoned contrary to law: the habeas corpus act points him out effectual means, as well to release himself, though committed even by the king in council, as to punish all those who shall thus unconstitutionally misuse him.’
Untersuchung der Rauchgewohnheiten und der Bereitschaft zum Rauchstopp bei Patienten einer internistischen Abteilung
Authors: Miedinger  , Drescher  , Nester  , Zeller  , von Garnier  , Leuppi
Published: April 2011

Rauchen ist einer der bedeutendsten vermeidbaren Risikofaktoren für die Entstehung von Lungen-, Herz-, Gefäss- und Krebserkrankungen. Wir berichten über eine prospektive Untersuchung betreffend das Rauchverhalten und den Willen zum Rauchstopp bei Patienten einer internistischen Klinik. Zwanzig Prozent der Teilnehmer gaben an, in den vorangegangenen 7 Tagen Zigaretten geraucht zu haben. Die Raucher waren häufiger männlichen Geschlechts und jünger als Nicht- oder Exraucher. Jeder zweite Raucher gab an, von einem Arzt bereits mindestens einmal zur Abstinenz aufgefordert worden zu sein, wobei nur einem Drittel eine aktive Unterstützung beim Rauchstopp angeboten wurde. Etwa die Hälfte der rauchenden Patienten war daran interessiert, mit dem Rauchen jetzt aufzuhören und an einem strukturierten Rauchstopp-Programm teilzunehmen. Nebst der Erfassung des Rauchstatus und des Aufhörwillens sollte den Patienten im Rahmen eines Spitalaufenthaltes eine pro-aktive Hilfe zum Rauchstopp angeboten werden.
Hilfe, ich habe krumme Finger – oder die Lösung einer Reihe medizinischer Phänomene
Authors: Rüst  , Knechtle
Published: April 2011

Wir beschreiben den Fall eines 23-jährigen Mannes, der selbst Humanmedizin studiert und während seiner Ausbildung durch das im Studium erlangte Wissen im Stande war, bei sich selbst die Verdachtsdiagnose eines Ehlers-Danlos-Syndroms zu stellen. Die Krankheit war im Vorfeld von mehreren Ärzten, die aufgrund der symptomalen Manifestationen konsultiert wurden, übersehen worden.
Fremdkörper in der Hohlhand – Holzsplitter unter den Beugesehnen
Authors: Lardi  , Glaab  , Friedl  , Mattli  , Ryf  , Loibl
Published: April 2011

Verletzungen im Bereich der Hände werden sehr häufig in Hausarztpraxen und Notfallstationen gesehen und betreffen meist die dominante Hand. Wir präsentieren einen Fall, bei dem nach initial frustraner Fremdkörpersuche durch den Hausarzt durch ausführliche Unfallanamnese, klinische Untersuchung und ergänzende Weichteilsonographie ein Hinweis auf eine Beugesehnenverletzung durch einen Fremdkörper gefunden wurde. Schaubilder veranschaulichen den Verletzungsmechanismus und betonen die Notwendigkeit des Verständnisses von Unfallkinematik und Unfallhergang. Bei Verdacht auf das Vorliegen eines Fremdkörpers im Bereich der Hand mit potentieller Sehnen-, Gefäss- oder Nervenbeteiligung ist die Beurteilung durch einen Handchirurgen zu empfehlen, der diese Verletzungen adäquat versorgen und die entsprechende Nachbehandlung gewährleisten kann.
Ecological and temperature controls on Mg/Ca ratios of Globigerina bulloides from the southwest Pacific Ocean
Authors: Marr Julene P. , Baker Joel A. , Carter Lionel , Allan Aidan S. R. , Dunbar Gavin B. , Bostock Helen C.
Published: April 2011

We present Mg/Ca data for Globigerina bulloides from 10 core top sites in the southwest Pacific Ocean analyzed by laser ablation inductively coupled plasma mass spectrometry (LA‐ICPMS). Mg/Ca values in G. bulloides correlate with observed ocean temperatures (7°C–19°C), and when combined with previously published data, an integrated Mg/Ca–temperature calibration for 7°C–31°C is derived where Mg/Ca (mmol/mol) = 0.955 × e0.068 × T (r2 = 0.95). Significant variability of Mg/Ca values (20%–30%) was found for the four visible chambers of G. bulloides, with the final chamber consistently recording the lowest Mg/Ca and is interpreted, in part, to reflect changes in the depth habitat with ontogeny. Incipient and variable dissolution of the thin and fragile final chamber, and outermost layer concomitantly added to all chambers, caused by different cleaning techniques prior to solution‐based ICPMS analyses, may explain the minor differences in previously published Mg/Ca–temperature calibrations for this species. If the lower Mg/Ca of the final chamber reflects changes in depth habitat, then LA‐ICPMS of the penultimate (or older) chambers will most sensitively record past changes in near‐surface ocean temperatures. Mean size‐normalized G. bulloides test weights correlate negatively with ocean temperature (T = 31.8 × e−30.5×wtN; r2 = 0.90), suggesting that in the southwest Pacific Ocean, temperature is a prominent control on shell weight in addition to carbonate ion levels.
Reduced Astrocytic Contribution to the Turnover of Glutamate, Glutamine, and GABA Characterizes the Latent Phase in the Kainate Model of Temporal Lobe Epilepsy
Authors: Alvestad Silje , Hammer Janniche , Qu Hong , Håberg Asta , Ottersen Ole Petter , Sonnewald Ursula
Published: April 2011

The occurrence of spontaneous seizures in mesial temporal lobe epilepsy (MTLE) is preceded by a latent phase that provides a time window for identifying and treating patients at risk. However, a reliable biomarker of epileptogenesis has not been established and the underlying processes remain unclear. Growing evidence suggests that astrocytes contribute to an imbalance between excitation and inhibition in epilepsy. Here, astrocytic and neuronal neurotransmitter metabolism was analyzed in the latent phase of the kainate model of MTLE in an attempt to identify epileptogenic processes and potential biomarkers. Fourteen days after status epilepticus, [1-13C]glucose and [1,2-13C]acetate were injected and the hippocampal formation, entorhinal/piriform cortex, and neocortex were analyzed by 1H and 13C magnetic resonance spectroscopy. The 13C enrichment in glutamate, glutamine, and γ-aminobutyric acid (GABA) from [1-13C]glucose was decreased in all areas. Decreased GABA content was specific for the hippocampal formation, together with a pronounced decrease in astrocyte-derived [1,2-13C]GABA and a decreased transfer of glutamine for the synthesis of GABA. Accumulation of branched-chain amino acids combined with decreased [4,5-13C]glutamate in hippocampal formation could signify decreased transamination via branched-chain aminotransferase in astrocytes. The results point to astrocytes as major players in the epileptogenic process, and 13C enrichment of glutamate and GABA as potential biomarkers.
MRI of bilateral sensorimotor network activation in response to direct intracortical stimulation in rats after unilateral stroke
Authors: van Meer Maurits PA , van der Marel Kajo , van der Sprenkel Jan Willem Berkelbach , Dijkhuizen Rick M
Published: April 2011

Reinstatement of perilesional activation and connectivity may underlie functional recovery after stroke. To measure activation responsiveness in perilesional cortex in relation to white matter integrity, we performed functional functional magnetic resonance imaging during stimulation of the contralesional cortex, together with diffusion tensor imaging, 3 and 28 days after stroke in rats. Despite disturbed sensorimotor function and abnormal callosal appearance at day 3, activation amplitudes were preserved in the perilesional sensorimotor cortex, although time-to-peak was significantly delayed. This indicates that in spite of dysfunction, perilesional cortical tissue can be activated subacutely after stroke, while delay of the hemodynamic activation response suggests impaired neurovascular coupling.
An overview of standby power management in electrical and electronic power devices and appliances to improve the overall energy efficiency in creating a green world
Authors: Chakraborty A. , Pfaelzer A.
Published: April 2011

With continuous global revolution toward the creation of a green environment, it is ardently necessary to eliminate all possible scopes of energy waste and leakage during the standby or inactive mode of operation. The magnitude of standby energy loss happening in all kinds of electronic and electrical systems is a global concern for scientists and engineers. A global picture of standby power consumption and reduction effort is elaborated in this paper. Approximate charts of standby power loss in majority of the electrical and electronic appliances are tabulated here. Numerous sources of energy losses in standby modes are identified in this paper. Some illustrations are made regarding the technical steps to be adhered to minimize the inactive mode power consumption. Power supplies that are the major contributors of energy waste are identified here. Various procedures and approaches are suggested, which would lead to standby power reduction and thereby would produce mode energy efficient systems. These corrective measures if properly implemented universally in both domestic as well as industrial appliances would save immense energy count and hence would reduce the global demand of energy.
Homogeneous dispersion of organic p-dopants in an organic semiconductor as an origin of high charge generation efficiency
Authors: Lee Jae-Hyun , Kim Hyun-Mi , Kim Ki-Bum , Kabe Ryota , Anzenbacher Pavel , Kim Jang-Joo
Published: April 2011

We report that an organic p-dopant tri[1,2-bis(trifluoromethyl)ethane-1,2-dithiolene] [Mo(tfd)3] resulted in higher density of holes than inorganic metal oxide dopants of ReO3 or MoO3 in 1,4-bis[N-(1-naphthyl)-N′-phenylamino]-4,4′-diamine even though the metal oxide dopants possess deeper work functions compared to Mo(tfd)3. Higher charge generation efficiency results largely from the homogeneous dispersion of Mo(tfd)3 in the host. In contradistinction, the transmission electron microscopy analysis revealed a formation of metal oxide nanoclusters. This highlights the importance of homogeneous dispersion for an efficient doping.
Numerical simulation of a liquid-metal flow in a poorly conducting pipe subjected to a strong fringing magnetic field
Authors: Albets-Chico X. , Radhakrishnan H. , Kassinos S. , Knaepen B.
Published: April 2011

Using high resolution numerical simulations, we study the flow of a liquid metal in a pipe subjected to an intense decreasing magnetic field (fringing magnetic field). The chosen flow parameters are such that our study is directly relevant for the design of fusion breeder blankets. Our objectives are to provide a detailed description of the numerical method and of the results for benchmarking purposes but also to assess the efficiency of the so-called “core flow approximation” that models liquid-metal flows under the influence of intense magnetic fields. Our results are in excellent agreement with available experimental measurements. As far as the pressure drop is concerned, they also match perfectly the predictions of the core flow approximation. On the other hand, the velocity profiles obtained in our numerical simulations show a significant departure from this approximation beyond the inflection point of the magnetic field’s profile. By plotting the momentum budget of the MHD equations, we provide evidence that this discrepancy can be attributed to the role of inertia that is neglected in the core flow approximation. We also consider a case with vanishing outlet magnetic field and we briefly illustrate the transition to turbulence arising in the outlet region of the pipe.
Rigorous coherent-structure theory for falling liquid films: Viscous dispersion effects on bound-state formation and self-organization
Authors: Pradas Marc , Tseluiko Dmitri , Kalliadasis Serafim
Published: April 2011

We examine the interaction of two-dimensional solitary pulses on falling liquid films. We make use of the second-order model derived by Ruyer-Quil and Manneville [Eur. Phys. J. B 6, 277 (1998); Eur. Phys. J. B 15, 357 (2000); Phys. Fluids 14, 170 (2002)] by combining the long-wave approximation with a weighted residual technique. The model includes (second-order) viscous dispersion effects which originate from the streamwise momentum equation and tangential stress balance. These effects play a dispersive role that primarily influences the shape of the capillary ripples in front of the solitary pulses. We show that different physical parameters, such as surface tension and viscosity, play a crucial role in the interaction between solitary pulses giving rise eventually to the formation of bound states consisting of two or more pulses separated by well-defined distances and traveling at the same velocity. By developing a rigorous coherent-structure theory, we are able to theoretically predict the pulse-separation distances for which bound states are formed. Viscous dispersion affects the distances at which bound states are observed. We show that the theory is in very good agreement with computations of the second-order model. We also demonstrate that the presence of bound states allows the film free surface to reach a self-organized state that can be statistically described in terms of a gas of solitary waves separated by a typical mean distance and characterized by a typical density.
Comparative studies on the magnetic properties of ZnS nanowires doped with transition metal atoms
Authors: Chen Hongxia , Shi Daning , Qi Jingshan
Published: April 2011

We comparatively studied the structural and magnetic properties of ZnS nanowires (NWs) doped with one or two transition-metal (TM) atoms (Cr, Mn, Fe, Co, and Ni) using first-principles calculations. The results indicate that the TM atoms prefer to be at the middle position of the NWs and have no tendency to form clusters. The formation energies of doped NWs were smaller than that of the pristine NW, indicating that doing process is an exothermic reaction. All of the NWs had atomlike magnetic moments mainly due to the 3d component of the TM atoms. Significant hybridization was observed between the d states of the TM atoms and the p states of the S atoms. Based on the half-metallic characteristic and long-range ferromagnetic interactions, we demonstrated that the ZnS NWs doped with Cr atoms have great potential for successful implementation into spintronic devices.
A simulation study on the combined effects of nanotube shape and shear flow on the electrical percolation thresholds of carbon nanotube/polymer composites
Authors: Eken A. E. , Tozzi E. J. , Klingenberg D. J. , Bauhofer W.
Published: April 2011

Here we investigate the combined effects of carbon nanotube (CNT) properties such as aspect ratio, curvature, and tunneling length and shear rate on the microstructure and electrical conductivities of CNT/polymer composites using fiber-level simulations. Electrical conductivities are calculated using a resistor network algorithm. Results for percolation thresholds in static systems agree with predictions and experimental measurements. We show that imposed shear flow can decrease the electrical percolation threshold by facilitating the formation of conductive aggregates. In agreement with previous research, we find that lower percolation thresholds are obtained for nanotubes with high aspect ratio. Our results also show that an increase in the curvature of nanotubes can make more agglomeration and reduce the percolation threshold in sheared suspensions.
Tuning energy levels in magnesium modified Alq3
Authors: Lin Chien-Hung , Chou Chi-Ta , Chen Yu-Hung , Wu Meng-Hsiu , Lee Jiun-Haw , Wu Chih-I , Chattopadhyay Surojit , Liu Chin-Hsin J. , Song Ker-Jar , Tai Yian , Wang Juen-Kai , Chen Kuei-Hsien , Chen Li-Chyong
Published: April 2011

The low molecular weight tris-(8-hydroxyquinoline) aluminum (Alq3) has been modified with magnesium (Mg) incorporation that altered the nature of its opto-electronic characteristics. Ultraviolet photoelectron spectroscopy and optical absorption measurements yielded quantitative energy positions of the electronic states of the Mg:Alq3, its highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO), and resultant shifts thereof due to the Mg incorporation. Consistent lowering of the HOMO and LUMO with Mg incorporation and a new distribution of the HOMO–LUMO separation are observed.
Nucleation properties of undercooled silicon at various substrates
Authors: Appapillai Anjuli T. , Sachs Christoph , Sachs Emanuel M.
Published: April 2011

When solidifying molten silicon in contact with a foreign substrate, the interfacial interaction between silicon and the substrate material can affect the nucleation behavior and therefore the final grain structure. This work illuminates the nucleation properties of different materials using differential scanning calorimetry to measure the undercooling below the melting temperature of molten silicon in contact with silicon oxides and nitrides. Both dry and wet thermal oxides show greater than 120 °C of undercooling before nucleation occurs, while silicon nitride consistently shows less than 17 °C. Variability in measured undercooling was minimized by improving coating uniformity but is not necessarily affected by overall sample deformation. A double-layer coating of silicon nitride over dry oxide reduced the dry oxide undercooling to <56 °C due to inter-layer thermal stresses, which can be minimized by reducing the outer layer of silicon nitride to <40 nm. The double-layer SiNx-SiO2 coating produced larger grains than the SiNx coating alone, when applied to a wafer recrystallization process.
Optical properties of gold and aluminium nanoparticles for silicon solar cell applications
Authors: Temple T. L. , Bagnall D. M.
Published: April 2011

The optical properties of metal nanoparticles are explored as a function of lateral size, shape, aspect-ratio and metal type. Simulations based on the discrete dipole approximation are compared with experimental measurements of arrays of metal nanoparticles fabricated by electron-beam lithography. Careful selection of experimental parameters ensures minimization of far-field and near-field coupling, and inhomogeneous broadening, thus allowing comparison with single particle simulations. The optical properties of Au nanoparticles are compared with similar Al nanoparticles for each particle type. For solar cell light-trapping applications, we require metal nanoparticles that exhibit extinction peaks near the band-edge region of the absorbing material, as well as low absorption and large optical cross-sections. Al nanoparticles are shown to be of interest for amorphous silicon solar cells, but their applications for polycrystalline solar cells is limited by the presence of an interband region in the near-infrared. The opposite is found for Au nanoparticles, which feature an interband threshold region in the visible that makes their optical properties unsuitable for amorphous silicon but very suitable for crystalline and polycrystalline silicon solar cells.
Single-mode fiber, velocity interferometry
Authors: Krauter K. G. , Jacobson G. F. , Patterson J. R. , Nguyen J. H. , Ambrose W. P.
Published: April 2011

In this paper, we describe a velocity interferometer system based entirely on single-mode fiber optics. This paper includes a description of principles used in developing the single-mode velocity interferometry system (SMV). The SMV design is based on polarization-insensitive components. Polarization adjusters are included to eliminate the effects of residual birefringence and polarization dependent losses in the interferometers. Characterization measurements and calibration methods needed for data analysis and a method of data analysis are described. Calibration is performed directly using tunable lasers. During development, we demonstrated its operation using exploding-foil bridge-wire fliers up to 200 m/s. In a final test, we demonstrated the SMV in a gas gun experiment up to 1.2 km/sec. As a basis for comparison in the gas gun experiment, we used another velocimetry technique that is also based on single-mode fiber optics: photonic Doppler velocimetry (PDV). For the gas gun experiment, we split the light returned from a single target spot and performed a direct comparison of the homodyne (SMV) and heterodyne (PDV) techniques concurrently. The two techniques had a negligible mean difference and a 1.5% standard deviation in the one-dimensional shock zone. Within one interferometer delay time after a sudden Doppler shift, a SMV unencumbered by multimode-fiber dispersion exhibits two color beats. These beats have the same period as PDV beats—this interference occurs between the “recently” shifted and “formerly unshifted” paths within the interferometer. We believe that recognizing this identity between homodyne and heterodyne beats is novel in the shock-physics field. SMV includes the conveniences of optical fiber, while removing the time resolution limitations associated with the multimode delivery fiber.
Contribution of carrier tunneling and gate induced drain leakage effects to the gate and drain currents of fin–shaped field–effect transistors
Authors: Garduño S. I. , Cerdeira A. , Estrada M. , Alvarado J. , Kilchytska V. , Flandre D.
Published: April 2011

The contribution of carrier tunneling and gate induced drain leakage (GIDL) effects in the total gate and drain currents of FinFET devices with different dimensions is analyzed. In order to fulfill this task, expressions for the leakage current due to carrier tunneling and GIDL effects at a Metal-Dielectric-Semiconductor structure were established and incorporated in the Symmetric Doped Double-Gate Model (SDDGM) for metal-oxide-semiconductor field-effect transistors (MOSFET). It is shown that both phenomena have to be taken into account for precise modeling of the device in all the operation regions although GIDL current can become predominant in the subthreshold region. The dependence of gate tunneling current in inversion and subthreshold regimes of operation is modeled as function of the applied voltages and transistor physical parameters by using analytical expressions. The present leakage current model is validated by comparing modeled with measured total gate and drain currents for FinFETs with different dimensions.
Linear stability analysis of ice growth under supercooled water film driven by a laminar airflow
Authors: Ueno Kazuto , Farzaneh Masoud
Published: April 2011

We propose a theoretical model for ice growth under a wind-driven supercooled water film. The thickness and surface velocity of the water layer are variable by changing the air stream velocity. For a given water supply rate, linear stability analysis is carried out to study the morphological instability of the ice-water interface. In this model, water and air boundary layers are simultaneously disturbed due to the change in ice shape, and the effect of the interaction between air and water flows on the growth condition of the ice-water interface disturbance is taken into account. It is shown that as the wind speed increases, the amplification rate of the disturbance is significantly affected by variable stresses exerted on the water-air interface by the air flow as well as restoring forces due to gravity and surface tension. We predict that an ice pattern of a centimeter-scale in wavelength appears and the wavelength decreases as the wind speed increases, and that the ice pattern moves in the direction opposite to the water flow. The effect of the air stress disturbance on the heat transfer coefficient at the water-air interface is also investigated for various wind speeds.
Field-assisted emission in AlGaN/GaN heterostructure field-effect transistors using low-frequency noise technique
Authors: Kayis Cemil , Zhu C. Y. , Wu Mo , Li X. , Özgür Ümit , Morkoç Hadis
Published: April 2011

We utilized low-frequency noise measurements to probe electron capture and emission from the traps in AlGaN/GaN heterostructure field-effect transistors as a function of drain bias. The excess noise-spectra due to generation-recombination effect shifted higher in frequency with the elevated temperature from room temperature up to 446 K. These temperature dependent noise measurements were carried out for four different drain-bias values from 4 up to 16 V with 4 V increments. The shift of the excess-noise in frequency was also seen with increasing drain bias. The characteristic recharging times for the trapped electrons varied within the range of 26 μs − 32 ms for the highest and lowest values of the drain voltage and temperature used in the experiment, respectively. The activation energies of the traps corresponding to the four different voltage values were extracted using temperature dependence by Arrhenius analysis. The trap energy at zero drain-bias was obtained as 0.71 eV by the extrapolation technique. This result suggests that the LFN is a very sensitive diagnostic tool to characterize trap states.
Exact solutions for a nonlinear model of dissipative media
Authors: Ruggieri Marianna , Valenti Antonino
Published: April 2011

Group classification of a mathematical model describing one-dimensional motion in nonlinear dissipative medium is performed. Reduced equations through the optimal system of subalgebras are obtained and some exact solutions are shown.
A simple parallel tandem organic solar cell based on metallophthalocyanines
Authors: Yuen Avery P. , Hor Ah-Mee , Preston John S. , Klenkler Richard , Bamsey Nathan M. , Loutfy Rafik O.
Published: April 2011

A simple parallel tandem solar cell based on a combination of Zn-phthalocyanine (Pc) and ClInPc has been fabricated and characterized. Compared to a traditional series tandem cell, parallel tandem cells eliminate the need for a semitransparent recombination layer, reducing the complexity of device fabrication while still providing an excellent increase in device performance. Results show a realized broadening of the spectral response and enhancement of the external quantum efficiency as a result of the complementary absorption profiles of ZnPc and ClInPc in the near infrared region. Introduction of a blended ClInPc:C60 layer is shown to more than double the power conversion efficiency of a standard ZnPc/C60 bilayer device (PCE=0.86%). The enhanced performance of the parallel tandem (PCE=1.81%) arises from an increase in both the open circuit voltage and the short circuit current.
Strong coupling between a photonic crystal nanobeam cavity and a single quantum dot
Authors: Ohta Ryuichi , Ota Yasutomo , Nomura Masahiro , Kumagai Naoto , Ishida Satomi , Iwamoto Satoshi , Arakawa Yasuhiko
Published: April 2011

We demonstrated the strong coupling between a one-dimensional photonic crystal nanobeam cavity and a single quantum dot (QD). Thanks to a high quality factor (∼25 000) with small mode volume [0.38×(n/λ)3] of the nanobeam cavity, an anticrossing behavior with a vacuum Rabi splitting of 226 μeV was observed. The ratio of the QD-cavity coupling strength to the cavity decay rate, which is a figure of merit of quantum optical applications, is estimated to 2.1. This is the highest value among any QD-based cavity quantum electrodynamics systems reported so far.
Center of quantum algebra $U_q^{\prime }({\rm so}_3)$Uq′( so 3)
Authors: Havlíček Miloslav , Pošta Severin
Published: April 2011

We analyze the structure of the center of the quantum algebra $U_q^{\prime }({\rm so}_3)$Uq′( so 3). This structure, as expected, depends substantially on the deformation parameter q. When q is not a root of unity, there exists only one Casimir element, which is the deformation of ordinary Casimir element known from so3. The center has a structure of a ring of polynomials of one variable. When qn = 1, there are three more Casimir elements of the form of polynomials in algebra generators. $U_q^{\prime }({\rm so}_3)$Uq′( so 3) can be seen as a finite dimensional module over the commutative ring of polynomials in these three Casimir elements. Knowing three-parametrical family of n-dimensional irreducible representations, we prove that the dimension of this module is n3. All four Casimir elements are no longer algebraically independent. We present the explicit description of the central variety, that is polynomial dependence between these four Casimir elements. This dependence differs for n = 2m + 1, n = 2(2m + 1) and n = 4m.
Electrical current mediated interconversion between graphene oxide to reduced grapene oxide
Authors: Teoh H. F. , Tao Y. , Tok E. S. , Ho G. W. , Sow C. H.
Published: April 2011

In this work, we demonstrate that graphene oxide (GO) can be reversibly converted to reduced-graphene-oxide (rGO) through the use of electric current. Strong electric field could cause ionization of water molecules in air to generate H+ ions at cathode, causing GO to be reduced. When the bias is reversed, the same electrode becomes positive and OH− ions are produced. According to Le Chatelier Principle, it then favors the reverse reaction, converting rGO back to GO, GO+2H++2e−=>rGO+H2O. X-ray spectroscopy and Raman spectroscopy were carried to verify the conversion reversibility in the reversed process.
Nanometer scale study of HfO2 trap states using single electron tunneling force spectroscopy
Authors: Winslow D. W. , Johnson J. P. , Williams C. C.
Published: April 2011

Standard methods to characterize trap states in dielectric films typically provide spatially averaged measurements. The development of single electron tunneling force spectroscopy has provided for the measurement of the energy of single trap states with atomic scale spatial resolution. In this letter, data taken on HfO2 films using this method is presented and discussed. Analysis of individual spectra shows that there is spatial variation in the density of trap states in these films. The spectra found by averaging data obtained from forty different locations shows good agreement with data taken via standard methods and with theoretical predictions.
Thermal characterization of MBE-grown GaN/AlGaN/GaN device on single crystalline diamond
Authors: Kuzmik J. , Bychikhin S. , Pogany D. , Pichonat E. , Lancry O. , Gaquière C. , Tsiakatouras G. , Deligeorgis G. , Georgakilas A.
Published: April 2011

Self-heating effects in a molecular beam epitaxy-grown GaN/AlGaN/GaN structure on a single crystalline diamond is investigated. A transient interferometric method, in combination with a three dimensional model, is used to describe a pulsed operation of a transistor-like heater, and a micro-Raman technique is used in a steady state. Good agreement is found between the techniques. The thermal conductivity of the diamond is found to be 2200 W/m K, and the thermal boundary resistance to the III-N epi-structure is < 1 × 10−8 m2 K/W. The excellent cooling efficiency of the diamond is manifested by the fast saturation of the temperature at 1 μs and by a record low normalized thermal resistance of 3.5 K mm/W.
Photoacoustic tomography in scattering biological tissue by using virtual time reversal mirror
Authors: Wu Dan , Tao Chao , Liu Xiaojun
Published: April 2011

On the basis of the time reversal invariance of photoacoustic waves, a photoacoustic tomography method using a virtual time reversal mirror is presented to tackle acoustical scattering in biomedical imaging. Simulations show its advantages over the traditional photoacoustic tomography method in imaging scattering tissues. The consideration of system errors guarantees its robustness in practical applications. The proposed method could serve as an alternative for imaging complex biological tissues, where strong scatterers such as bones and cavities exist.
Oxadiazole host for a phosphorescent organic light-emitting device
Authors: Chiu Tien-Lung , Lee Pei-Yu , Lee Jiun-Haw , Hsiao Chih-Hung , Leung Man-Kit , Lee Chung-Chieh , Chen Chen-Yu , Yang Chih-Chiang
Published: April 2011

In this paper, we demonstrate a phosphorescent organic light-emitting device (OLED) with enhanced current efficiency (in terms of cd/A) based on an oxadiazole (OXD) derivative as the electron-transporting host of the emitting layer (EML) doped with a phosphorescent dopant, iridium(III)bis[4,6-(di-fluorophenyl)-pyridinato-N, C2′] picolinate (FIrpic). The maximum current efficiency of OXD-based OLEDs was 13.0 cd/A. Compared to the phosphorescent OLED with a conventional hole-transporting host, 1,3-bis(carbazol-9-yl)benzene (mCP) with 11.1 cd/A in maximum current efficiency, 17.2% improvement was achieved. However, in terms of external quantum efficiency (EQE), the OXD- and mCP-based OLEDs were 4.01 and 4.66%, respectively, corresponding to a 13.9% decrease. Such a discrepancy can be understood from the electroluminescence (EL) variation. Contrary to the hole-transporting mCP, OXD exhibited electron transporting characteristics which shifted the recombination zone toward the anode. The optical interference effect result was that the relative intensity at long wavelengths (500–600 nm) was higher in the OXD-based OLED, which was more sensitive to the human eye and increased the current efficiency, even though the EQE was lower. Besides, in OXD-OLED, the recombination zone shifted toward the anode side with a high driving voltage, which was also deduced from the EL spectral variations. Under a high driving voltage, we observed the relative intensity of FIrpic emission ata longer wavelength increased which resulted from the optical interference effect, and emission from the hole-transporting layer increased. By using hole-transporting mCP and electron-transporting OXD as the hosts of double EML (DEML), the maximum current-efficiency and EQE of the optimized DEML-OLED further increases to 17.6 cd/A and 7.06%, which corresponds to improvements of 58.6% and 51.5%, compared to the single mCP-OLED, and by 35.4% and 76.1%, compared to the single OXD-OLED, respectively. This was a result of the better charge balance in DEML, and less quenching effects from transporting materials.
Effects of a step-graded AlxGa1−xN electron blocking layer in InGaN-based laser diodes
Authors: Zhang Yun , Kao Tsung-Ting , Liu Jianping , Lochner Zachary , Kim Seong-Soo , Ryou Jae-Hyun , Dupuis Russell D. , Shen Shyh-Chiang
Published: April 2011

A step-graded AlxGa1-xN electron blocking layer (EBL) is studied on InGaN-based laser diodes (LDs). Its efficacy on device performance is investigated with respect to stimulated emission properties, internal quantum efficiency, internal loss, and temperature-dependent characteristics. When compared to a LD structure with an abrupt Al0.18Ga0.82N EBL design, the LD with the step-graded AlxGa1-xN EBL design demonstrates lower threshold current density and higher slope efficiency. The threshold current density is reduced from 4.6 kA/cm2 to 2.5 kA/cm2 under pulsed-current operation and the corresponding slope efficiency is increased from 0.72 W/A to 1.03 W/A. The insertion of the step-graded AlxGa1−xN EBL leads to a dramatic enhancement in internal quantum efficiency from 0.60 to 0.92, while internal loss keeps at 9 ∼ 10 cm−1. The temperature-dependent measurement also shows that the step-graded AlxGa1−xN EBL can improve the thermal stability with reduced red-shift from 0.05 nm/K to 0.034 nm/K. This simple yet efficient structural design change provides an effective way to achieve high-performance InGaN-based LDs with higher optical-output power and lower electric-power consumption.
A novel compact design of calibration equipment for gas and thermal sensors
Authors: Feng P. X. , Zhang H. X. , Peng X. Y. , Sajjad M. , Chu J.
Published: April 2011

A novel design of calibration equipment has been developed for static and dynamic calibrations of gas and thermal sensors. This system is cheap, compact, and easily adjustable, which is also combined with a plasma surface modification source for tailoring the surface of sensors to ensure the sensitivity and selectivity. The main advantage of this equipment is that the operating temperature, bias voltage, types of plasma source (for surface modification), types of feeding gases, and gas flow rate (for calibrations), etc., can be independently controlled. This novel system provides a highly reliable, reproducible, and economical method of calibrations for various gas and thermal sensors.
Characteristics of stand-alone microlenses in fiber-based fluorescence imaging applications
Authors: Mirkhalaf M. , Murukeshan V. M. , Beng Tor Shu , Shinoj V. K. , Sathiyamoorthy K.
Published: April 2011

Microlens-ended fibers, which have found tremendous interest in the recent past, find potential biomedical applications, in particular, in endoscopic imaging. The work presented in this paper focuses on the stand-alone microlenses along with custom-fabricated specialty optical fiber, such as imaging fiber, for probe imaging applications. Stand-alone self-aligned microlenses have been fabricated employing microcompression molding and then attached at the end facet of imaging fiber. A detailed characterization of the fabricated microlens is carried and it demonstrates appropriate focusing ability, high fluorescence collection efficiency and imaging ability for biomedical applications. The surface roughness of the microlens is found to be 25 nm with a minimum spot size of 38 μm. The probe imaging system is found to be able to image the fluorescence microspheres of 10 μm size. The collection efficiency of the fiber probe with lens found to be enhanced by three times approximately.