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Cluster computers are dominating high performance computing (HPC) today. The success of this architecture is based on the fact that it proffits from the improvements provided by mainstream computing well known under the label of Moore's law. But trying to get to Exascale within this decade might require additional endeavors beyond surfing this technology wave. In order to find possible directions for the future we review Amdahl's and Gustafson's thoughts on scalability. Based on this analysis we propose an advance architecture combining a Cluster with a so called Booster element comprising of accelerators interconnected by a high performance fabric. We argue that this architecture provides significant advantages compared to today's accelerated clusters and might pave the way for clusters into the era of Exascale computing. The DEEP project has been presented aiming for an implementation of this concept. Six applications from fields having the potential to exploit Exascale systems will be ported to DEEP.We analyze one application in detail and explore the consequences of the constraints of the DEEP systems on its scalability.

We analyze a single-particle Mach-Zehnder interferometer experiment in which the path length of one arm may change (randomly or systematically) according to the value of an external two-valued variable $x$, for each passage of a particle through the interferometer. Quantum theory predicts an interference pattern that is independent of the sequence of the values of $x$. On the other hand, corpuscular models that reproduce the results of quantum optics experiments carried out up to this date show a reduced visibility and a shift of the interference pattern depending on the details of the sequence of the values of $x$. The proposed experiment will show that: (1) it can be described by quantum theory, and thus not by the current corpuscular models, or (2) it cannot be described by quantum theory but can be described by the corpuscular models or variations thereof, or (3) it can neither be described by quantum theory nor by corpuscular models. Therefore, the proposed experiment can be used to determine to what extent quantum theory provides a description of observed events beyond the usual statistical level., Accepted for publication in J. Phys. Soc. Jpn

International audience; Organic thin-film transistor (OTFT) devices were achieved using the laser-induced forward transfer technique. As p-type organic semiconductor, distyryl-quaterthiophene (DS4T) was vacuum-deposited on a donor substrate and transferred with picosecond laser pulses on Si/SiO2-based receiver substrates to form an organic active layer. To avoid laser damage of the organic thin film, a UV-sensitive aryltriazene polymer as a sacrificial layer was used. The polymer layer, deposited on the donor substrate prior to the organic layer deposition, has high absorption at the laser wavelength and does not contaminate the printed pixels. The DS4T pixels printed on receiver substrates have well defined morphological properties as shown by atomic force microscopy and scanning electronic microscopy. OTFT devices were characterized in top- and bottom-contact configurations using thermally evaporated gold lines as source-drain electrodes. DS4T pixels printed as active layer for charge transport not only issue mobility values comparable to DS4T layers prepared by vacuum evaporation but also a relative electrical stability over time. (C) 2011 Elsevier B.V. All rights reserved.

By using lattice QCD computations we determine the sigma terms and strangeness content of all octet baryons by means of an application of the Hellmann-Feynman theorem. In addition to polynomial and rational expressions for the quark mass dependence of octet members, we use SU(3) covariant baryon chiral perturbation theory to perform the extrapolation to the physical up and down quark masses. Our N_f=2+1 lattice ensembles include pion masses down to about 190 MeV in large volumes (M_\pi L > 4), and three values of the lattice spacing. Our main results are the nucleon sigma term \sigma_{\pi N} = 39(4)(^{+18}_{-7}) and the strangeness content y_{N} = 0.20(7)(^{+13}_{-17}). Under the assumption of validity of covariant baryon \chi PT in our range of masses one finds y_{N} = 0.276(77)(^{+90}_{-62})., Comment: LaTeX. 15 pages, 5 figures. Text and results corrected according to Erratum [Phys. Rev. D 93, 039905(E) (2016)]

We study the dispersion relations of mesons and baryons built from Brillouin quarks on one N_f=2 gauge ensemble provided by QCDSF. For quark masses up to the physical strange quark mass, there is hardly any improvement over the Wilson discretization, if either action is link-smeared and tree-level clover improved. For quark masses in the range of the physical charm quark mass, the Brillouin action still shows a perfect relativistic behavior, while the Wilson action induces severe cut-off effects. As an application we determine the masses of the \Omega_c^0, \Omega_{cc}^+ and \Omega_{ccc}^{++} baryons on that ensemble., Comment: 16 pages, 9 figures, 4 tables; v2: one Reference added, matches published version

We report on the semi-quantitative analysis of pulsed laser induced plasma species as well as thin film compositions of La0.6Sr0.4MnO3 grown on SrTiO3 substrates under various background pressure regimes using an 18O isotope labelled La0.6Sr0.4MnO3 target. The importance of negative metal–oxygen or positive metal–oxygen ions to influence the final oxygen composition of the thin film is illustrated through the use of mass spectrometry, where the chemical reactions between the laser ablated target species with the oxygen background molecules are directly characterized. We find that the influence of metal–oxygen negative ions is not as important as the metal–oxygen positive ions to the final oxygen composition of the LSMO film, due to their low stability in high background partial pressures. Furthermore, we observe that the oxygen incorporated in La0.6Sr0.4MnO3 thin films coming from the target is ~44%, 29% and 1% at 2 × 10−3 mbar, 1 × 10−2 mbar and 2 × 10−1 mbar, respectively. When growing films at 10−1 mbar on 18O2 exchanged substrates, almost all oxygen originates from the background and almost none from the substrate or target.

PM3 and AM1 semiempirical molecular orbital techniques are used to establish a model for internal rotation about the N{sub 2}-N{sub 3} axis of 1-aryl-3,3-dialkyltriazines. The PM3 method is satisfactory for obtaining agreement between the experimental and calculated results, but the AM1 method has an artifact in the potential energy curve of internal rotation about the N{sub 2}-N{sub 3} axis. 24 refs., 6 figs., 5 tabs.

At the precision reached in current lattice QCD calculations, electromagnetic effects are becoming numerically relevant. Here, electromagnetic effects are included by superimposing $\mathrm{U}(1)$ degrees of freedom on $N_f = 2+1$ QCD configurations from the Budapest-Marseille-Wuppertal Collaboration. We present preliminary results for the electromagnetic corrections to light pseudoscalars mesons masses and discuss some of the associated systematic errors., Comment: 7 pages, 2 figures, The XXIX International Symposium on Lattice Field Theory, July 10-16, 2011, Squaw Valley, Lake Tahoe, California, USA

We investigate how the topological charge density in lattice QCD simulations is affected by violations of chiral symmetry caused by the fermion action. To this end we compare lattice configurations generated with a number of different actions including first configurations generated with exact dynamical overlap quarks. We visualize the topological profiles after mild smearing. In the topological charge correlator we measure the size of the positive core, which is known to shrink to zero extension in the continuum limit. To leading order we find the core size to scale linearly with the lattice spacing with the same coefficient for all actions, even including quenched simulations. In the subleading term the different actions vary over a range of about 10 %. Our findings suggest that non-chiral lattice actions at current lattice spacings do not differ much for observables related to topology, both among themselves and compared to overlap fermions., 9 pages, 7 figures, two column layout, updated to match published version

A status report is given for a joint project of the Budapest-Marseille-Wuppertal collaboration and the Regensburg group to study the quark mass-dependence of octet baryons in SU(3) Baryon XPT. This formulation is expected to extend to larger masses than Heavy-Baryon XPT. Its applicability is tested with 2+1 flavor data which cover three lattice spacings and pion masses down to about 190 MeV, in large volumes. Also polynomial and rational interpolations in M_\pi^2 and M_K^2 are used to assess the uncertainty due to the ansatz. Both frameworks are combined to explore the precision to be expected in a controlled determination of the nucleon sigma term and strangeness content.

International audience; Laser-induced forward transfer (LIFT) has been used to deposit pixels of an organic semiconductor, distyryl-quaterthiophenes (DS4T). The dynamics of the process have been investigated by shadowgraphic imaging for the nanosecond (ns) and picosecond (ps) regime on a time-scale from the laser iradiation to 1.5 mu s. The morphology of the deposit has been studied for different conditions. Intermediate sacrificial layer of gold or triazene polymer has been used to trap the incident radiation. Its role is to protect the layer to be transferred from direct irradiation and to provide a mechanical impulse strong enough to eject the material. (C) 2010 Elsevier B.V. All rights reserved.

International audience

Over the last 20 years, the open-source community has provided more and more software on which the world’s high-performance computing systems depend for performance and productivity. The community has invested millions of dollars and years of effort to build key components. However, although the investments in these separate software elements have been tremendously valuable, a great deal of productivity has also been lost because of the lack of planning, coordination, and key integration of technologies necessary to make them work together smoothly and efficiently, both within individual petascale systems and between different systems. It seems clear that this completely uncoordinated development model will not provide the software needed to support the unprecedented parallelism required for peta/ exascale computation on millions of cores, or the flexibility required to exploit new hardware models and features, such as transactional memory, speculative execution, and graphics processing units. This report describes the work of the community to prepare for the challenges of exascale computing, ultimately combing their efforts in a coordinated International Exascale Software Project.

The numerous properties of liposomes, i.e., non- toxicity, biodegradability, and their ability to encapsulate different biological active substances in aqueous and lipid phase, make them perfect models of biomembranes. Lipo- somes made up of phospholipids may be used to study new applications such as cell targeting or, under specific experi- mental conditions, may be applied in micro and nano-sized biosensors. This study demonstrates the capability of direct laser printing of liposomes in micron-scale patterns for the real- ization of biosensors or drug delivery systems. The transfer experiments were carried out onto ordinary glass substrates, and optical microscopy images reveal that well-defined patterns without splashes can be obtained for a narrow range of laser transfer fluences using 193 nm irra- diation and an intermediate triazene polymer. The triazene polymer with different thicknesses was used as sacrificial layer with the purpose of protecting the liposome solution

Laser-induced forward transfer (LIFT) has been used to print 0.6 mm × 0.5 mm polymer light-emitting diode (PLED) pixels with poly[2-methoxy, 5-(2-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV) as the light-emitting polymer. The donor substrate used in the LIFT process is covered by a sacrificial triazene polymer (TP) release layer on top of which the aluminium cathode and functional MEH-PPV layers are deposited. To enhance electron injection into the MEH-PPV layer, a thin poly(ethylene oxide) (PEO) layer on the Al cathode or a blend of MEH-PPV and PEO was used. These donor substrates have been transferred onto both plain indium tin oxide (ITO) and bilayer ITO/PEDOT:PSS (poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) blend) receiver substrates to create the PLED pixels. For comparison, devices were fabricated in a conventional manner on ITO substrates coated with a PEDOT:PSS hole-transporting layer. Compared to multilayer devices without PEO, devices with ITO/PEDOT:PSS/MEH-PPV:PEO blend/Al architecture show a 100 fold increase of luminous efficiency (LE) reaching a maximum of 0.45 cd/A for the blend at a brightness of 400 cd/m(2). A similar increase is obtained for the polymer light-emitting diode (PLED) pixels deposited by the LIFT process, although the maximum luminous efficiency only reaches 0.05 cd/A for MEH-PPV:PEO blend, which we have attributed to the fact that LIFT transfer was carried out in an ambient atmosphere. For all devices, we confirm a strong increase in device performance and stability when using a PEDOT:PSS film on the ITO anode. For PLEDs produced by LIFT, we show that a 25 nm thick PEDOT:PSS layer on the ITO receiver substrate considerably reduces the laser fluence required for pixel transfer from 250 mJ/cm(2) without the layer to only 80 mJ/cm(2) with the layer.

Magnetic monopole currents are believed to have a strong impact on the Monte Carlo dynamics of compact quantum electrodynamics near the phase transition. We have indications that updating algorithms have to form and to break up monopole current clusters in order to force the tunneling of the system between the coexisting phases, the confined phase and the Coulomb phase. This might be responsible for long lived metastabilities in the time series. We present parallel numerical algorithms which allow the fast identification of clusters of monopole loops, the determination of their topological properties as well as their visualization in the course of a Monte Carlo simulation. The algorithms are implemented on the Connection Machine CM-5. We compare the data parallel programming style with a message passing approach. Complexity and performance are discussed.

In the photochemical decomposition of triazene R-N=N-NR 1 R 2 in CH 3 CN solutions, where R was (3-HOOC-, di-3,5-HOOC-, 4-HOOC-, 4-CN-)phenyl and R 1 , R 2 were -CH 3 , -C 2 H 5 , -CH(CH 3 ) 2 , -CH 2 CH 2 OH, the corresponding phenyl-substituted radicals were identified as 5,5-dimethyl-1-pyrroline N-oxide (DMPO) or (CH 3 ) 3 CNO adducts. The reaction is described by a first-order kinetics with a half lifetime of 7 s. If R was di-3,5-CON 3 -C 6 H 3 -, a nitrogen-centred radical was found on radiation in the solid state as well as in CH 3 CN solution with DMPO as spin trap

Triazene compounds have recently attracted attention due to a variety of interesting properties. The cytostatic activity discovered for several substituted triazenes *) has stimulated intense research efforts directed towards the development of triazene-based drugs3). In view of the importance of this field, several reviews on the synthesis of triazenes are available4-’). A second class of applications is based on the fact that the triazeno group is comparatively stable with respect to thermal decomposition, but undergoes facile photo-chemical cleavage releasing nitrogen. This property, which may lead to novel applications in photolithography and photoreproduction, is the motivation for the present study. Photopolymers which can be structured by light are important materials in the microelectronics industry. Laser ablation of polymers ‘3 ’) has been intensively investigated in this context; the laser treatment represents a dry processing technique, without the need for wet processing steps. Powerful XeC1*-excimer lasers emitting at 308 nm are available for reliable large-scale industrial operation, making it desirable to use this wavelength in polymer ablation. However, many polymers suitable for application in microelectronics do not absorb at this wavelength. Therefore, progress has been made recently in sensitizing these polymers for ablation at 308 nm, by the addition of low-molecular-weight chromophors. Acridine lo), benzophenone ‘ I ) , pyrene 12), porphyrines 1 3 ) and 1,3-diphenyltriazenes 143 15) have been tested for this purpose. Recently, we have successfully used and characterized several l-phenyl-3,3-dialkyltriazenes as dopants for the ablation of poly(methy1 methacrylate) (PMMA) at 308 nm 16). An attractive alternative to physical doping is the incorporation of the triazeno group into the polymer itself. Recently, polymer-analogous reactions have been used to synthesize a PMMA copolymer containing ca. 0,3 mol-Vo of triazene side chains ”). In the present communication, we are investigating the synthesis of another novel type of photopolymer which contains two triazeno groups per repeating unit. Synthesis is carried out by a polycondensation reaction in which a bis-diazonium salt and a

In numerical simulations, compact quantum electrodynamics exhibits a weakly first-order phase transition. On large lattice sizes, using conventional updating algorithms, this goes along with strong metastabilities near the location of the phase transition. The relative weight of the two phases cannot be marked out accurately enough within a reasonable amount of simulation time. We discuss a phenomenological method that allows to determine the relative weight between the phases in principle with great precision. Our method is expected to give reliable results for any system exhibiting a similar phase transition pattern.

Numerical simulations of quantum electrodynamics near the phase transition suffer from an extreme slowing down on large lattices. The two leading terms of the decaying autocorrelation function can be attributed to the influence of first-order phase transition effects, called supercritical slowing down, and second-order phase transition effects, called critical slowing down, respectively. We show that we can bypass supercritical slowing down using a conventional local updating algorithm based on a phenomenological weight ratio fixing method. As for critical slowing down, we apply a new global multi-scale updating algorithm which removes critical slowing down completely. We compare the structure of the local vs. the global algorithm as well as their implementation on the Connection Machine CM-2, analyze their computational complexity and present actual performance measurements.

Planar shocks generated by short pulse lasers are useful in studies of shock compression phenomena and may have applications in materials science, biology, and medicine. We have found the fluence profiles of 120–400 fs duration Gaussian spatial mode incident laser pulses are reproducibly flattened via surface optical breakdown and Kerr focusing in thin dielectric substrates at fluences just above the ablation threshold. These flat laser profiles have been used to produce planar shocks that are flat to 0.7 nm root-mean-square over a 75–100 μm diameter.

Molecular geometries, electronic transitions, bond orders, and dipole moments are calculated for 19 l-aryl3,3-diethyltriazenes and two 3-alkyl- 1 ,5-diarylpentazadienes, using standard AM1 and PM3 semiempirical methods. Calculated UV spectra compare well with the experimental results, A strong correlation is established between the barrier to internal rotation, AG*, and the N2-N3 bond order. The photochemical decomposition of substituted triazenes and pentazadienes is of interest in view of their application as promoters in laser-induced polymer ablation. Therefore, the photolysis quantum yields at 308 nm are investigated in various solvents. The influence of substituents on the aryl moiety on the quantum yield is analyzed in terms of a correlation with the calculated N1=N2 bond order. The effects of different nitrogen-bound alkyl substituents on the photochemical decomposition behavior can be represented by a similar correlation. Differences between the photolysis behavior of triazene and pentazadiene derivatives are discussed.

LASER ablation propulsion (LAP) is a major new electric propulsion concept with a 35-year history. In LAP, an intense laser beam [pulsed or continuous wave (CW)] strikes a condensedmatter surface (solid or liquid) and produces a jet of vapor or plasma. Just as in a chemical rocket, thrust is produced by the resulting reaction force on the surface. Spacecraft and other objects can be propelled in this way. In some circumstances, there are advantages for this technique compared with other chemical and electric propulsion schemes. It is difficult to make a performance metric for LAP, because only a few of its applications are beyond the research phase and because it can be applied in widely different circumstances that would require entirely different metrics. These applications range from milliwatt-average-power satellite attitude-correction thrusters through kilowatt-average-power systems for reentering near-Earth space debris and megawatt-to-gigawatt systems for direct launch to lowEarth orbit (LEO). We assume an electric laser rather than a gas-dynamic or chemical laser driving the ablation, to emphasize the performance as an electric thruster. How is it possible for moderate laser electrical efficiency to givevery high electrical efficiency? Because laser energy can be used to drive an exothermic reaction in the target material controlled by the laser input, and electrical efficiency only measures the ratio of exhaust power to electrical power. This distinction may seem artificial, but electrical efficiency is a key parameter for space applications, in which electrical power is at a premium. The laser system involved in LAP may be remote from the propelled object (on another spacecraft or planet-based), for example, in laser-induced space-debris reentry or payload launch to low planetary orbit. In other applications (e.g., the laser–plasma microthruster that we will describe), a lightweight laser is part of the propulsion engine onboard the spacecraft.

This article presents a short review of the use of triazene polymer as a dynamic release layer (DRL) for laser-induced forward transfer (LIFT), before looking at the latest research in more detail. The field of triazene polymer ablation only started around 20 years ago and has grown rapidly into a number of different application areas. Most promisingly, triazene ablation has been refined as a method for propulsion, bringing the benefits of LIFT to the deposition of sensitive transfer materials. The key to understanding LIFT with a triazene DRL is to understand the more fundamental nature of triazene polymer ablation in both frontside and backside orientations. This article focuses on the most recent experimental results on LIFT with a triazene DRL: the effect of picosecond pulse lengths compared with nanosecond pulse lengths; the effect of reduced air pressure; and the improvements in transfer in terms of range of transfer materials, and transfer across a gap. The results all help improve fundamental understanding of triazene-based LIFT, and the transfer of functioning OLEDs demonstrates the capability of the technique.

Laser Ablation Propulsion is a broad field with a wide range of applications. We review the 30‐year history of laser ablation propulsion from the transition from earlier pure photon propulsion concepts of Oberth and Sanger through Kantrowitz’s original laser ablation propulsion idea to the development of air‐breathing “Lightcraft” and advanced spacecraft propulsion engines. The polymers POM and GAP have played an important role in experiments and liquid ablation fuels show great promise. Some applications use a laser system which is distant from the propelled object, for example, on another spacecraft, the Earth or a planet. Others use a laser that is part of the spacecraft propulsion system on the spacecraft. Propulsion is produced when an intense laser beam strikes a condensed matter surface and produces a vapor or plasma jet. The advantages of this idea are that exhaust velocity of the propulsion engine covers a broader range than is available from chemistry, that it can be varied to meet the instantaneous demands of the particular mission, and that practical realizations give lower mass and greater simplicity for a payload delivery system. We review the underlying theory, buttressed by extensive experimental data. The primary problem in laser space propulsion theory has been the absence of a way to predict thrust and specific impulse over the transition from the vapor to the plasma regimes. We briefly discuss a method for combining two new vapor regime treatments with plasma regime theory, giving a smooth transition from one regime to the other. We conclude with a section on future directions.

One of the most versatile deposition techniques in solid-state physics and analytical chemistry is the vaporization of condensed matter using photons. A short-pulsed high-power laser beam is focused onto a sample surface thereby converting a finite volume of a solid instantaneously into its vapor phase constituents such as ions and neutrals. Subsequently, the vapor moves away from the target at a high velocity and can be sampled either to grow a film or being analyzed by various spectroscopic techniques. In this chapter, the focus is on general properties of pulsed laser ablation relevant for solid-state physics like the initial ablation processes, plume formation, and plume properties. Next, oxide thin film growth will be discussed and the growth of LaAlO3/SrTiO3 heterostructures is presented as one example of tailoring oxide interfaces with surprising properties. The final discussion is on the topic of polymer ablation.

This contribution investigates laser‐induced damage of thin film and bulk polymer samples, with the focus on physical processes occurring close to the damage threshold. In‐situ real‐time reflectivity (RTR) measurements with picosecond (ps) and nanosecond (ns) temporal resolution were performed on thin polymer films on a timescale up to a few microseconds (μs). A model for polymer thin film damage is presented, indicating that irreversible chemical modification processes take place already below the fluence threshold for macroscopic damage. On dye‐doped bulk polymer filters (as used for laser goggles), transmission studies using fs‐and ps‐laser pulses reveal the optical saturation behavior of the material and its relation to the threshold of permanent damage. Implications of the sub‐threshold processes for laser safety applications will be discussed for thin film and bulk polymer damage.

The presence of strong metastabilities in computer simulations of models showing a first order phase transition hinders a reliable determination of the weight ratio between the two phases. We discuss a new phenomenological method which allows an accurate fixing of the weight ratio using the standard multihistogram procedure.

We describe how the multihistogram method can be used to get reliable results from simulations in the critical region of first-order transitions even in the presence of severe hysteresis effects.

Using the Connection Machine CM-2 we investigate critical slowing down for the multi-scale update algorithm (MSU) for abelian gauge theories recently proposed by two of the present authors. From our measurements on four-dimensional U(1) gauge theory on 84 and 164 lattices, we find the critical exponent z for MSU dynamics to be consistent with zero. For reference, and as a test of our analysis technique, we verified that the Metropolis local update algorithm (LU) exhibits the random walk value z ≅ 2.

Autocorrelation becomes an increasingly important tool to verify improvements in the state of the simulational art in Latice Gauge Theory. Semi-systolic and full-systolic algorithms are presented which are intensively used for correlation computations on the Connection Machine CM-2. The semi-systolic algorithm makes use of an intrinsic, microprogrammed global-add reduction function which is implemented extremely well on the Connection Machine. Nevertheless, the full-systolic correlation algorithm which makes use only of local communication and computation operations turns out to be substantially superior to the semi-systolic scheme whose basic step involved a non-local sum computation that extends over the entire machine.

UV laser ablation of polymers is a versatile method to structure polymers with high resolution. The mechanism of ablation is often discussed controversially, but it is necessary to keep in mind that polymers are complex systems with a wide variety of properties that can influence the ablation mechanism. Analyzing the data, it appears that the ablation mechanism is a complex interrelated system, where photochemical and photothermal reactions are very important. The pressure jump, which is associated with the creation of small molecules and originates from both types of reaction, is also important for ablation. The importance of each effect is strongly dependent on the type of polymer, the laser wavelengths, the pulse length, and the substrate. UV laser ablation can also be utilized to deposit directly thin polymer films by PLD, but this is limited to certain polymers. Alternative laser-based techniques (LIFT) utilize the decomposition of a thin layer to transfer complete layers with high spatial resolution. This approach can be used to transfer pixels of sensitive materials to a substrate with a minimal thermal and UV load.

Recently, more and more e-science projects require resources in more than one production e-science infrastructure, especially when using HTC and HPC concepts together in one scientific workflow. But the interoperability of these infrastructures is still not seamlessly provided today and we argue that this is due to the absence of a realistically implementable reference model in Grids. Therefore, the fundamental goal of this paper is to identify requirements that allows for the definition of the core building blocks of an interoperability reference model that represents a trimmed down version of OGSA in terms of functionality, is less complex, more fine-granular and thus easier to implement. The identified requirements are underpinned with gained experiences from world-wide interoperability efforts.

Perovskite-type N-substituted SrTiO3 thin films with a preferential (001) orientation were grown by pulsed laser deposition on (001)-oriented MgO and LaAlO3 substrates. Application of N2 or ammonia using a synchronized reactive gas pulse produces SrTiO3-x:Nx films with a nitrogen content of up to 4.1 at.% if prepared with the NH3 gas pulse at a substrate temperature of 720 °C. Incorporating nitrogen in SrTiO3 results in an optical absorption at 370-460 nm associated with localized N(2p) orbitals. The estimated energy of these levels is ≈2.7 eV below the conduction band. In addition, the optical absorption increases gradually with increasing nitrogen content., Materials, 2 (3), ISSN:1996-1944

More than 99% of the mass of the visible universe is made up of protons and neutrons. Both particles are much heavier than their quark and gluon constituents, and the Standard Model of particle physics should explain this difference. We present a full ab-initio calculation of the masses of protons, neutrons and other light hadrons, using lattice quantum chromodynamics. Pion masses down to 190 mega electronvolts are used to extrapolate to the physical point with lattice sizes of approximately four times the inverse pion mass. Three lattice spacings are used for a continuum extrapolation. Our results completely agree with experimental observations and represent a quantitative confirmation of this aspect of the Standard Model with fully controlled uncertainties., Comment: 22 pages, 3 Tables, 8 Figures. Published in Science (21 November 2008) with Supporting Online Material. Submission to arXiv has been delayed by 6 months to respect the journal's embargo policy

Due to the strong collective deceleration during the initial stage of relativistic heavy-ion collisions, the nuclear matter irradiates real and virtual bremsstrahlung. We describe the process of bremsstrahlung emission in the framework of a semiclassical model in order to study coherence and incoherence effects in the production process. Guided by the intuitive notation of shock fronts being formed between the incident nuclei, we use a simple parametrization of the nuclear current density. The photon spectrum is studied up to photon energies of 300 MeV. In particular, a gradual transition from the coherent production process of low-energy photons to the incoherent one for hard photons is demonstrated. For heavy collision systems coherence effects in the photon spectra dominate, showing characteristic structures arising from shock fronts. The dilepton spectrum is described in first-order perturbation theory. Generally, dileptons are found to be produced incoherently. Only in the case of dielectron production with small invariant pair masses do moderate coherence effects survive.

The aryl coupling reaction of bromobenzene on alumina-supported copper catalysts has been studied as model for dioxin formation. The reaction was monitored in situ by transmittance FTIR spectroscopy. Time-dependent changes in the spectra were recorded during addition of bromobenzene to the carrier gas stream. Both coupling of phenyl intermediates to yield biphenyls and formation of phenol and phenolate were observed. Novel approaches to inhibit the coupling reaction or aryl halides by addition of ethanolamine to the catalyst surface were studied. The resulting inhibition was attributed to site blocking and irreversible deactivation of the copper surface due to imine and nitride formation.

In this note we suggest an experimental proof for testing whether the photon production by bremsstrahlung in relativistic heavy ion collisions can be described in terms of a classical nuclear current density or not. We propose to measure not only the mean number of photons with a given energy, but also the corresponding root mean square deviation of it. A classical description of the current density is possible if the squared deviation is equal to the mean number of photons.

Laser ablation of polyaniline in its conducting and isolating form revealed very similar ablation properties upon irradiation at 308 nm. Both types of polymer film can be structured with high resolution at high fluences. The ablation craters have sharp contours and no debris contaminates the surrounding area. At low fluences the creation of cone structures is observed. X-ray photoelectron spectroscopy reveals the carbonization of the surface upon laser ablation. As preferred decomposition sites the imine groups in doped and undoped polyaniline are identified.

Various physical and chemical processes which are involved in laser-induced backside wet etching are investigated. The surface of quartz etched by the laser-induced backside wet etching using a XeCl excimer laser at various fluences is analyzed by Raman microscopy, X-ray photoelectron spectroscopy and fiber-tip attenuated total-reflection Fourier-transform infrared spectroscopy. The investigations reveal the formation of a high amount of amorphous carbon deposits at low laser fluences, which strongly adhere to the quartz surface. Combining X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy reveals that the quartz is also chemically and structurally modified due to a loss of oxygen and by a change of the quartz polymorph at intermediate and high laser fluences. These modification and their differences for different fluences are explained by the etching mechanisms itself, i.e. different magnitudes of temperature and pressure jumps. The results show clearly which conditions for etching must be applied to machine high-quality structures, e.g. micro-optical elements in quartz.

The application of energetic polymers has resulted in an increased thrust in micro laser plasma thrusters compared to standard polymers. In this study we tested a novel concept for micro laser plasma thrusters, i.e. the application of liquid polymeric fuels, by using polymer solutions of the energetic materials with different viscosity. Shadowgraphy experiments suggest that for higher viscosity solutions ablation without splashing is possible, indicating that liquids are applicable as fuels in laser plasma thrusters. First thrust measurements on a viscous polymer solution confirmed this by yielding a specific impulse similar to a solid material.

The Hybrid Monte Carlo (HMC) algorithm currently is the favorite scheme to simulate quantum chromodynamics including dynamical fermions. In this talk-which is intended for a non-expert audience--I want to bring together methodical and practical aspects of the HMC for full QCD simulations. I will comment on its merits and shortcomings, touch recent improvements and try to forecast its efficiency and role in future full QCD simulations.

Applied Physics A, 93 (3), ISSN:0947-8396, ISSN:1432-0630, ISSN:0340-3793