bluuebunny/crossref_metadata_2025_split huggingface dataset:
Production of Exploding Materials for Detonators: Control of Crystal Growth of Lead and Barium 2,4,6‐trinitroresorcinate
Authors: Orbovic Nikola , Codoceo Cristian Lorca 
Published: October 2008

AbstractThe production of lead and barium 2,4,6‐trinitroresorcinate in a suitable form for loading by gravity in detonator production has been investigated. During the work, we discovered that the synthesis of the mentioned salts in the presence of some crystal habit additives gives such characteristics of the products. A goal of our work was to investigate the role of some crystal growth additives in the nucleation, growth, size, and shape of lead 2,4,6‐trinitroresorcinate and barium 2,4,6‐trinitroresorcinate crystals. Among several crystal growth additives mentioned in the bibliography, we chose carboxymethylcellulose (sodium salt, viscosity 3–4 Pa⋅s), polyvinyl alcohol, as well as two new ones, cationic acrylamide copolymer salt, polyelectrolyte AS‐3605 and acrylic acid–acrylamide copolymer salt, Haicat (PraestrolR 835BS). As a synthesis pattern, we chose an aqueous procedure of synthesis, using solutions of lead(II) or barium salts and magnesium 2,4,6‐trinitroresorcinate. The crystal growth additives were added to one of the solutions, depending on their nature. During the research, most of the attention was focused on crystal size and shape, on safety handling and manipulation, as well as on the yield and process performing facility. The final products were qualified by chemical (Pb and NO2 group contents) and physical (crystal shape and size, bulk density, flowability, and impact and friction sensitivity) analyses.
Estimating Heats of Detonation and Detonation Velocities of Aromatic Energetic Compounds
Authors: Keshavarz Mohammad Hossein 
Published: October 2008

AbstractA new method is introduced to predict reliable estimation of heats of detonation of aromatic energetic compounds. At first step, this procedure assumes that the heat of detonation of an explosive compound of composition CaHbNcOd can be approximated as the difference between the heat of formation of all H2OCO2 arbitrary (H2O, CO2, N2) detonation products and that of the explosive, divided by the formula weight of the explosive. Overestimated results based on (H2OCO2 arbitrary) can be corrected in the next step. Predicted heats of detonation of pure energetic compounds with the product H2O in the liquid state for 31 aromatic energetic compounds have a root mean square (rms) deviation of 2.08 and 0.34 kJ g−1 from experiment for (H2OCO2 arbitrary) and new method, respectively. The new method also gives good results as compared to the second sets of decomposition products, which consider H2, N2, H2O, CO, and CO2 as major gaseous products. It is shown here how the predicted heats of detonation by the new method can be used to obtain reliable estimation of detonation velocity over a wide range of loading densities.
Time‐resolved photoluminescence study of mesoporous ZnO nanostructures
Authors: Schwalm Michael , Horst Swantje , Chernikov Alexej , Rühle Wolfgang W. , Lautenschläger Stephan , Klar Peter J. , Meyer Bruno K. , Waitz Thomas , Tiemann Michael , Chatterjee Sangam 
Published: October 2008

AbstractWe report a systematic study of the photoluminescence properties of ZnO nanostructures. In particular, mesoporous ZnO powders of varying surface‐to‐mass ratio are investigated and compared to a bulk reference. At low temperatures the emission from higher‐energy states is very pronounced and even dominant for samples with high surface‐to‐mass ratio. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Emission properties of ZnSe‐based pillar microcavities at elevated temperatures
Authors: Kalden Joachim , Lohmeyer Henning , Sebald Kathrin , Meeser Thomas , Gutowski Jürgen , Kruse Carsten , Gust Arne , Hommel Detlef , Wiersig Jan , Jahnke Frank 
Published: October 2008

AbstractWe present research achievements that advance the development of quantum dot based low threshold vertical cavity surface emitting lasers operating at elevated temperatures. We report on the optical properties of monolithic ZnSe‐based pillar microcavities. Measurements were performed on different microcavity structures containing either ZnCdSSe quantum wells or CdSe quantum dots, respectively, as their active region. For the quantum dot based structures, the implementation of additional MgS/ZnSSe barriers yield temperature stability of the quantum dot emission up to room temperature. Microphotoluminescence experiments show an enhanced collection efficiency for the quantum dot emission in spectral resonance with an optical microcavity mode.High quality factors of up to Q = 7860 were achieved for quantum dot structures, while for quantum well devices Q = 3500 was reached as being analyzed by microphotoluminescence and micro‐reflectivity spectroscopy. For the quantum well structures, single mode stimulated emission at 510 nm is shown at 280 K under pulsed optical excitation. Threshold reduction with decreasing pillar diameter is observed in accordance to numerical calculations based on microscopic laser theory. The results are promising for the realization of efficient quantum dot based low threshold vertical cavity surface emitting laser devices operating at elevated temperatures in the near future. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mott transition of excitons in ZnSe studied by phase resolved reflection
Authors: Manzke Günter , Henneberger Klaus , Seemann Matthias , Stolz Heinrich 
Published: October 2008

AbstractThe Mott transition of excitons in a semiconductor with increasing carrier density is in principle well understood as a consequence of screening of the Coulomb interaction between carriers. While the position of the exciton stays widely unchanged the exciton peak disappears due to band gap shrinkage. However, a more quantitative check of applied theoretical models for the screening and of the role of quantum kinetic effects in this process is still open.We demonstrate that the phase‐resolved reflection in shallow‐confined ZnSSe heterostructures opens the possibility of a detailed study of the Mott transition due to the appearance of pronounced interferences effects of propagating polariton modes.Our theoretical approach for the investigation of the influence of excited carriers on the dielectric susceptibility is based (i) on a quasi‐particle approximation for the carrier energies and damping, and (ii) on the semiconductor Bloch equations including dynamical screening and a quantum kinetic treatment of scattering. These manybody effects lead to drastic changes of both amplitude and phase of the reflected light: Jumps of the phase are steepened, show abrupt changes from +π to –π and are smoothed out, and interference peaks in the amplitude decrease and disappear completely with increasing excitation. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ga(AsSb)/GaAs/(AlGa)As heterostructures: additional hole‐confinement due to quantum islands
Authors: Horst S. , Chatterjee S. , Hantke K. , Klar P. J. , Nemeth I. , Stolz W. , Volz K. , Bückers C. , Thränhardt A. , Koch S. W. , Rühle W. , Johnson S. R. , Wang J.‐B. , Zhang Y.‐H. 
Published: October 2008

AbstractFormation of self‐organized Ga(AsSb) quantum‐islands during growth is shown to occur in a series of Ga(AsSb)/GaAs/(AlGa)As heterostructures, resulting in an in‐plane hole confinement of several hundred meV. The shape of the in‐plane confinement potential is nearly parabolic and thus yields almost equidistant hole energy levels. Transmission electronmicroscopy reveals that the quantum islands (QIs) are 100 nm in diameter and exhibit an inplane variation of the Sb concentration of more than 30%, which is the origin of the confinement. Up to seven bound hole states are observed in the photoluminescence spectra. Time‐resolved photoluminescence data are shown as function of excitation density. The influence of size and density of such structures as well as the mechanisms of growth are discussed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Performance changes of a vertical‐external‐cavity surfaceemitting laser by an intra‐cavity anti‐reflex‐coating
Authors: Horst S. , Chatterjee S. , Rühle W. , Brick P. , Diehl W. , Stolz W. , Kühn E. , Thränhardt A. , Koch S. W. 
Published: October 2008

AbstractThe influence of an intra‐cavity anti‐reflection coating on the switch‐on dynamics and the power input‐output characteristic of a vertical‐external‐cavity surface‐emitting laser (VECSEL) system are investigated. The experiments show a significantly higher threshold and slower switch‐on dynamics for anti‐reflection coated systems.These differences originate in the changes in the mode strength at the active medium due to the more or less pronounced sub‐cavity. The presented simulations based on microscopic calculations are in good qualitatively agreement with the experiments. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interband vs. intersubband polaritons and the relevance of quantum confinement
Authors: Pereira Mauro F. 
Published: October 2008

AbstractThis paper presents a numerical study of the dependence of the coupling between light and intersubband transitions in quantum wells with respect to electronic quantum confinement. Different quantum wells are analysed and it is shown that intersubband polaritons and antipolaritons can be made more stable that interband polaritons by adjusting the intersubband population differences. This flexibility in control is no possible in the interband excitonic case and may be crucial for THz polaritonic‐based devices. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quantum condensation in electron–hole plasmas
Authors: Semkat D. , Kremp D. , Henneberger K. 
Published: October 2008

AbstractQuantum condensation phenomena occur in Bose systems (Bose–Einstein condensation, BEC) as well as in strongly degenerate Fermi systems (BCS state). In Fermi systems with Bose‐like bound states both phenomena are possible.A theoretical approach to describe quantum condensation in electron‐hole plasmas in the framework of realtime Green's functions is presented. The resulting phase boundary shows that there is a smooth crossover from BEC to BCS. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetooptical properties of quantum disks in the Faraday configuration
Authors: Schillak P. , Czajkowski G. 
Published: October 2008

AbstractWe show how to compute the optical functions (the complex magneto‐susceptibility, dielectric function, magneto‐reflection spectra) for semiconductor quantum disks exposed to a uniform magnetic field in the growth direction, including the excitonic effects. The optical response is calculated for an electromagnetic wave propagating in the growth direction, i.e. the wavevector is parallel to the static magnetic field, which corresponds to the so‐called Faraday configuration. The method uses the microscopic calculation of nanostructure excitonic wave functions and energy levels, and the macroscopic real density matrix approach to compute the electromagnetic fields and susceptibilities.The electron‐hole screened Coulomb potential is adapted. The novelty of our approach is that the solution is obtained in terms of known one‐particle electron and hole eigenfunctions, since, in the considered nanostructure due to confinement effects accompanied by the e‐h Coulomb interaction, the separation of the relativeand center‐of‐mass motion is not possible. We obtain both the eigenvalues and the eigenfunctions. The convergence of the proposed method is examined. Numerical calculations have been performed for In0.55Al0.45As (disk)/ Al0.35Ga0.65As (barrier) disks. Good agreement with experiments has been obtained. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Motional enhancement of the exciton magnetic moment
Authors: Kochereshko V. P. , Platonov A. V. , Davies J. J. , Wolverson D. , Smith L. C. , Cox R. T. , Cibert J. , Mariette H. 
Published: October 2008

AbstractIn this paper we demonstrate that the magnetic moment of the exciton increases by an order of magnitude due to its motion along the magnetic field. The effect was observed for a set of quantum well structures with different well widths and based on various semiconductor compounds. The reason for this effect is mixing of the exciton's center of mass motion and the internal motion of electron and hole in the exciton. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Trion states in a dense 2DEG
Authors: Kochereshko V. P. , Klochikhin A. A. , Crooker S. A. , Karczewski G. , Kossut J. 
Published: October 2008

AbstractPhotoluminescence spectra taken from modulationdoped CdTe/(Cd0.7Mg0.3)Te quantum well structures with a two‐dimensional electron gas of moderate to high density (from ne ∼ 1010 up to ne ∼ 1012 cm–2) in magnetic fields from 0 T to 45 T were studied. The observed spectra were analyzed in terms of combined excitonelectron processes. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Semiconductor laser based THz generation and detection
Authors: Brenner Carsten , Hoffmann Stefan , Friedrich Claus‐Stefan , Schlauch Tobias , Klehr Andreas , Erbert Götz , Tränkle Günther , Jördens Christian , Salhi Mohammed , Koch Martin , Hofmann Martin R. 
Published: October 2008

AbstractWe present different concepts for compact and cost effective THz technology based on semiconductor diode lasers. First, we discuss THz sources starting with modelocked diode lasers for time domain THz sampling, and two‐colour diode lasers for continuous wave THz generation. Then we show how THz radiation can be generated directly out of two‐colour diode lasers and discuss possible schemes for an optimisation of this effect towards application relevant power levels. Finally, we demonstrate that diode lasers can also serve as detectors for THz radiation. We couple the emission of a THz gas laser into the active region of a diode laser and demonstrate that this leads to a variation of the voltage over the p‐n‐junction which is almost proportional to the THz power coupled into the device. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ultrafast dynamics and interlayer thermal coupling of hot carriers in epitaxial graphene
Authors: Sun Dong , Wu Zong‐Kwei , Divin Charles , Li Xuebin , Berger Claire , Heer Walt A. de , First Phillip N. , Norris Theodore B. 
Published: October 2008

AbstractWe report the first application of nondegenerate ultrafast pump‐probe spectroscopy to investigate the dynamics of hot Dirac Fermions in epitaxial graphene. The DT spectra can be understood in terms of the effect of hot thermal carrier distributions on interband transitions with no electron‐hole interaction. We also investigate the thermal coupling between carriers of doped and undoped layers. The coupling time is found to be below 500fs. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Gain characteristics and lasing of Ga(NAsP) multi‐quantum well structures
Authors: Lange C. , Chatterjee S. , Kunert B. , Volz K. , Stolz W. , Rühle W. W. , Gerhardt N. C. , Hofmann M. R. 
Published: October 2008

AbstractLasing is demonstrated for a Ga(NAsP) multi quantumwell structure grown pseudomorphically on GaP using metal‐organic vapour‐phase epitaxy. For a series of temperatures ranging from 8 K to 290 K, the sample emission characteristics are determined. With increasing pump power, a spectral narrowing of the emitted light along with a blue‐shift is observed as the lasing threshold is approached.Above the threshold, the emission splits up spectrally into a pattern of clearly distinguishable modes. In addition, the potential of this material concerning roomtemperature lasing is investigated by means of a variable stripe‐length experiment, where a modal gain of 10 cm–1 is observed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Variance decomposition approach to the prediction of the seasonal mean circulation: Comparison with dynamical ensemble prediction using NCEP's CFS
Authors: Zheng X. , Straus D. M. , Frederiksen C. S. 
Published: October 2008

AbstractReanalysis data and a recently developed variance decomposition approach are applied to empirically predict seasonal mean 500 hPa geopotential height anomalies in both the Northern and Southern Hemisphere from the beginning of each season. The predictors are only several popular tropical SST indices and the annular mode indices at one month or one season lead. The statistical prediction is compared with the dynamical ensemble prediction of the National Centers for Environmental Prediction's coupled Climate Forecast System (CFS). It is found that their skills are quite comparable. The advantages and disadvantages of dynamical prediction and statistical prediction are discussed. A strategy for a new statistical–dynamical prediction which combines the advantages of both statistical and dynamical predictions is suggested. Copyright © 2008 Royal Meteorological Society
Ionisation in the absence of high voltage using supercritical fluid chromatography: a possible route to increased signal
Authors: Thite Mohini A. , Boughtflower Robert , Caldwell Jeff , Hitzel Laure , Holyoak Clare , Lane Stephen J. , Oakley Paul , Pullen Frank S. , Richardson Stefan , Langley G. John 
Published: October 2008

AbstractSupercritical fluid chromatography (SFC) is fast becoming a technique of choice for the analysis of a wide range of compounds and has been found to be complementary to high‐performance liquid chromatography (HPLC). The combination of SFC and mass spectrometry (MS) affords a very useful tool in the separation and analysis of compounds. In this study the ionisation of samples in the absence of an applied electrospray voltage has been observed when using SFC/MS, with some compounds showing increased sensitivity when all ionisation source high voltage (HV) is removed. In an attempt to understand the mechanism of ionisation, a series of test compounds were analysed using standard electrospray ionisation (ESI) and atmospheric pressure chemical ionisation (APCI) source configurations and also different API source designs. In both cases, data were acquired with the applied high voltage on (normal conditions) or with the high voltage off, i.e. no voltage spray (novo‐spray). The standards were analysed with a range of pressure and modifier percentage conditions. To understand the nature of the ionisation process observed, this was compared with three established liquid‐to‐gas ionisation mechanisms. These were thermospray (TSP), charge residue model (CRM) of ESI and sonic spray ionisation (SSI). Experiments were undertaken in an attempt to explain this ionisation phenomenon and quantify any observed change in sensitivity. The most important point to note is that enhanced ionisation was observed under novo‐spray conditions in a SFC/MS configuration, which in certain cases provides a lowering in the overall limit of detection (LOD). Copyright © 2008 John Wiley & Sons, Ltd.
A robotic assistant for stereotactic neurosurgery on small animals
Authors: Ramrath L. , Hofmann U. G. , Schweikard A. 
Published: October 2008

AbstractBackgroundThis work presents the development and performance analysis of a robotic system for stereotactic neurosurgery on small animals. The system is dedicated to the precise placement of probes in the small animal brain, thus providing an improved framework for brain research.MethodsBased on an analysis of small animal stereotaxy, the mechanical design of the robotic system is presented. Details of the structure and mechanical components and a kinematic description are outlined. The calibration process of the system for arbitrary probes is described. To analyse the mechanical positioning accuracy of the system, a testbed is presented.ResultsPositioning performance results show that the system features a mean mechanical positioning accuracy of 32 µm and a mean positioning repeatability of 11 µm.ConclusionThe system meets the requirements of targeting small functional areas within the brain of small animals and thus offers a new tool for small animal brain research. Copyright © 2008 John Wiley & Sons, Ltd.
An active endoscopic robot based on wireless power transmission and electromagnetic localization
Authors: Li Hongwei , Yan Guozheng , Ma Guanying 
Published: October 2008

AbstractBackgroundConventional endoscopes have the disadvantages of causing pain to patients because of their large dimensions and allowing incomplete inspection because of their limited power.MethodsAn active inchworm‐like endoscopic robot has been designed, which is based on electromagnetic localization and synthesis of magnetic field strength vectors.ResultsThe efficiency of wireless power transmission can be kept above 0.9% when the power‐receiving coil is at arbitrary position and orientation. The position error of localization is < 10 mm and the average error of orientation angle is 2° . When the robot moves through part of the porcine colon, images are transmitted outwards continuously at a speed of 30 fps and the temperature rise of the colon is < 1 °C. By simulation, the electromagnetic exposures to the human body are lower than international standards.ConclusionsThe endoscopic robot is a promising tool for use by doctors, although further experiments and improvements need to be done. Copyright © 2008 John Wiley & Sons, Ltd.
The MARVIN message authentication code and the LETTERSOUP authenticated encryption scheme
Authors: Simplicio Marcos A. , Barbuda Pedro d'Aquino F. F. S. , Barreto Paulo S. L. M. , Carvalho Tereza C. M. B. , Margi Cintia B. 
Published: October 2008

AbstractWe present MARVIN, a new parallelizable message authentication code (MAC) based on the ALRED family. The new algorithm is designed with resource‐constrained platforms inmind and explores the structure of an underlying block cipher toprovide security at a small cost in terms of memory needs. Also,we show how MARVIN can be used as an authentication‐onlyfunction or else in an authenticated encryption with associateddata (AEAD) scheme. We define a new AEAD proposal called LETTERSOUP, which is based on the mode ofoperation. Finally, we LFSRC analyze the security and performance of theresulting schemes. Copyright © 2008 John Wiley & Sons, Ltd.
Information depth determination for hard X‐ray photoelectron spectroscopy up to 15 keV photoelectron kinetic energy
Authors: Rubio‐Zuazo J. , Castro G. R. 
Published: October 2008

AbstractIn the present work, we have determined the information depth in a solid for hard X‐ray photoelectron spectroscopy (HAXPES) up to a photoelectron kinetic energy of 15 keV. For that, we have followed the evolution of the photoemission signal from different core levels of a gold overlayer grown in situ on a polycrystalline copper substrate as a function of the photoelectron kinetic energy. We demonstrate that in the case of gold, an information depth of 57 nm can be achieved by detecting photoelectrons with 15‐keV kinetic energy. The photoemission signal produced at this depth corresponds to 0.2% of the signal coming from a semi‐infinite solid bulk. Such a high sensitivity can only be reached with the combination of a third‐generation synchrotron radiation beam with a high‐transmission electron analyzer. Copyright © 2008 John Wiley & Sons, Ltd.