bluuebunny/crossref_metadata_2025_split huggingface dataset:
Selective photochemical etching of GaN films and laser lift‐off for microcavity fabrication
Authors: Trichas E. , Xenogianni C. , Kayambaki M. , Tsotsis P. , Iliopoulos E. , Pelekanos N. T. , Savvidis P. G. 
Published: September 2008

AbstractWavelength dependent photochemical etching of GaN films reveals strong dependence of the photocurrent on the excitation wavelength. Sharp increase in the photocurrent with increasing photon energy is attributed to the onset of absorption above the GaN bandgap. The etching rate of GaN films strongly correlates with the measured photocurrent. No photocurrent and etching is observed for AlGaN films under same conditions. The method could pave the way to the development of truly selective self‐stop etching of GaN on AlGaN yielding smooth surfaces for the fabrication of GaN based microcavities. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Internal friction investigation of reverse martensitic transformation in oil‐quenched Ni64Al36 alloy
Authors: Zhou Z. C. , Yan Y. J. , Zhong M. 
Published: September 2008

AbstractLow‐frequency internal friction investigation of reverse martensitic transformation in oil‐quenched Ni64Al36 alloy has been carried out using a multifunctional internal friction apparatus from room temperature to 400 °C and additionally differential scanning calorimetry and X‐ray diffraction experiments were also completed. It has been shown that an internal friction peak presents at about 220 °C in the internal friction–temperature curve during heating for the oil‐quenched Ni64Al36 alloy but not for the furnace‐cooled Ni64Al36 alloy. The peak still appears during cooling and the peak temperature shifts to lower temperature. The changes of the peak temperature positions cannot be visibly observed when the vibration frequency is changed. The peak heights increase with decreasing vibration frequency and increasing heating rate, being linearly directly proportional to $ \dot T / f $ It has been suggested that the internal friction peak results from reverse martensitic transformation of L10 → γ during heating and originates from martensitic transformation of γ → L10 during the subsequent cooling process. The influence of the thermal cycles on the transformation is not observed for the limited thermal cycles. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Superlensing with plane plates consisting of dielectric cylinders in glass envelopes
Authors: Foca E. , Sergentu V. V. , Daschner F. , Tiginynau I. M. , Ursaki V. V. , Knöchel R. , Föll H. 
Published: September 2008

AbstractThe approach of designing negative‐refractive‐index materials on the basis of dielectric rods with a gradient of the dielectric constant is tested experimentally. A triangular‐lattice plane‐parallel slab assembled from multilayer dielectric rods with a refractive index approximating a fish‐eye profile is shown to exhibit excellent focusing properties for the TM polarized electromagnetic radiation at frequencies defined by the structural parameters of the slab. A clearly defined super‐resolution effect is observed at corresponding frequencies, the width of the focal spot down to a quarter of the wavelength being achieved. The experimental data are partially verified by simulations which show a very good match to the measurements. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Föhn as a response to changing upstream and downstream air masses
Authors: Mayr Georg J. , Armi Laurence 
Published: September 2008

AbstractObservations of föhn from the field phase of the Mesoscale Alpine Programme (MAP) are used to study how differences between the air masses upstream and downstream of the central Alpine crest determine whether the flow can descend to the lee as either shallow föhn, when it passes through passes in the mountains, or deep föhn, when it overflows the Alpine crest. First, the föhn case of 30 October 1999 is examined using ECMWF analyses and radiosonde data at various upstream and downstream locations. Additional measurements from aircraft, dropsondes, an instrumented car and automatic weather stations are then used for a detailed study of the föhn flow across the Brenner Pass. Advection of cold air around the eastern edges of the Alps and warm air around the western edge of the Alps ahead of a synoptic ridge set up a reservoir of colder air on the south side of the Alps and a reservoir of warmer air to the north. The depth to where the air was colder on the southern side was sufficient for a shallow föhn to flow through the pass. After the passage of the ridge axis, synoptic cold air advection provided another source of colder air, this time from the southwest, growing deeper with time and having a synoptically imposed cross‐barrier flow component. The maximum depth to where the air upstream was colder than downstream extended just above the peaks of the highest mountains. An analysis of the detailed measurements across the Brenner Pass showed that this depth was also the top of the layer that descended and accelerated down the lee slopes of the Wipp Valley. Upstream, air above the föhn layer had an even stronger cross‐barrier component yet did not descend because it did not have lower potential temperatures than the downstream side at that level. Deep föhn never developed.An examination of other well‐documented MAP föhn cases confirmed the conclusion from the 30 October event that shallow and deep föhns – at least for the central Alps – are mostly a response to differences in air masses between the upstream and downstream side. A cross‐barrier component of the flow was only a modification but in itself not sufficient to cause the flow to both descend and accelerate down the lee slope, unless potential temperatures on the upstream side were lower in this layer than on the downstream side. Copyright © 2008 Royal Meteorological Society
The Monte Carlo Independent Column Approximation: an assessment using several global atmospheric models
Authors: Barker H. W. , Cole J. N. S. , Morcrette J.‐J. , Pincus R. , Räisänen P. , von Salzen K. , Vaillancourt P. A. 
Published: September 2008

AbstractThe Monte Carlo Independent Column Approximation (McICA) computes domain‐average, broadband radiative flux profiles within conventional global climate models (GCMs). While McICA is unbiased with respect to the full ICA, it generates, as a by‐product, random noise. If this by‐product leads to statistically significant impacts on GCM simulations, it could limit the usefulness of McICA. This paper assesses the impact of McICA's random noise on six GCMs. To this end, the GCMs performed ensembles of 14‐day long simulations for various renditions of McICA, each with differing amounts of random noise. As seen in the past, low‐cloud fraction and surface temperature were affected most by noise. However, all GCM simulations using operationally viable renditions of McICA showed no statistically significant impacts, even for precipitation ‐ a highly intermittent variable that one might expect to be sensitive to random fluctuations. Two GCMs showed statistically significant responses using an academic version of McICA that generates overly large sampling noise. Time series analyses of high‐resolution (i.e. typically 2‐hourly) data revealed that fluctuations associated with most variables and GCMs are immune to McICA noise. Moreover, the nature of these fluctuations can vary substantially among GCMs and most often they overwhelm any noise impacts. Overall, the results presented here corroborate a range of previous studies done on one GCM at a time: random noise produced by recommended versions of McICA has statistically insignificant effects on GCM simulations. Copyright © 2008 Royal Meteorological Society and Her Majesty in Right of Canada.
Lessons learnt from the operational 1D + 4D‐Var assimilation of rain‐ and cloud‐affected SSM/I observations at ECMWF
Authors: Geer Alan J. , Bauer Peter , Lopez Philippe 
Published: September 2008

AbstractRain‐ and cloud‐affected Special Sensor Microwave/Imager (SSM/I) observations are assimilated operationally at the European Centre for Medium‐Range Weather Forecasts (ECMWF). The four‐dimensional variational analysis (4D‐Var) assimilates total column water vapour (TCWV) derived from one‐dimensional variational retrievals (1D‐Var). From the SSM/I radiances, 1D‐Var retrieves surface wind and the vertical profiles of temperature, humidity, cloud and precipitation. The main shortcoming of the ‘1D + 4D‐Var’ technique is that, of all this information, only TCWV gets into the 4D‐Var analysis. More information could be used: the rainwater path agrees well, in an instantaneous comparison, with observations from the precipitation radar on the Tropical Rainfall Measuring Mission. There are other issues, however: the simplified moist physics operators used in 1D‐Var produce roughly twice the observed amount of rain, but the problem is masked by a sampling bias, which comes from applying 1D + 4D‐Var when the observations are cloudy or rainy, but not when the first guess is rainy or cloudy and the observations are clear. The shortcomings of 1D + 4D‐Var will be addressed by moving to a direct 4D‐Var assimilation which includes all SSM/I observations, whether clear, cloudy or rainy, in the same stream. Copyright © 2008 Royal Meteorological Society
Evaluation of the variational soil moisture assimilation scheme at Deutscher Wetterdienst
Authors: Hess Reinhold , Lange Martin , Wergen Werner 
Published: September 2008

AbstractA two‐dimensional, variational soil moisture assimilation scheme has been in operational use at DWD since 2000. The same scheme was also used and evaluated in the EU‐funded project ELDAS. By design, the scheme leads to improved forecasts of screen level parameters. The present paper discusses if this is achieved in a physically consistent way so that the assimilation process results in more realistic soil water contents. It is shown that overall the scheme behaves well, both in the longer‐term mean and in individual cases. A remarkable result is that the assimilation process for soil moisture also leads to improved quality of precipitation forecasts. Nevertheless, erroneous precipitation forecasts remain the largest error source for soil moisture. The assimilation scheme can successfully compensate for these errors. Using observed precipitation would be better still.The diagnostics also revealed some unwanted features. They include sometimes large and frequent assimilation changes in the lower layer of the soil model. Reasons for this are discussed and possible remedies suggested. Copyright © 2008 Royal Meteorological Society
A mass‐conservative version of the semi‐implicit semi‐Lagrangian HIRLAM
Authors: Lauritzen P. H. , Kaas E. , Machenhauer B. , Lindberg K. 
Published: September 2008

AbstractA mass‐conservative version of the semi‐implicit semi‐Lagrangian High‐Resolution Limited‐Area Model (HIRLAM) is presented. The explicit continuity equation is solved with the so‐called cell‐integrated semi‐Lagrangian (CISL) method. To allow for long time steps, the CISL scheme is coupled with a recently developed semi‐implicit time‐stepping scheme that involves the same non‐complicated elliptic equation as in HIRLAM. Contrarily to the traditional semi‐Lagrangian method, the trajectories are backward in the horizontal and forward in the vertical, i.e. cells moving with the flow depart from model layers and arrive in a regular column, and their vertical displacements are computed from continuity of mass and hydrostatic balance in the arrival column. This involves just two‐dimensional upstream integrals and allows for a Lagrangian discretization of the energy conversion term in the thermodynamic equation.Preliminary validation of the new model version is performed using an idealized baroclinic wave test case. The accuracy of the new formulation of HIRLAM is comparable to the reference version though it is slightly more diffusive. A main finding is that the new discretization of the energy conversion term leads to more accurate simulations compared to the traditional ‘Eulerian’ treatment. Copyright © 2008 Royal Meteorological Society
Using a neural network to benchmark a diagnostic parametrization: the Met Office's visibility scheme
Authors: Claxton B. M. 
Published: September 2008

AbstractWithin the Met Office's Unified Model the visibility is diagnosed from a set of the model's prognostic variables using a parametrization. This parametrization has been optimized to minimize the error in the model visibility, relative to observed visibility. The performance of the parametrization is dependant on two aspects; (1) the quality of the input meteorological variables and (2) the structure of the parametrization itself. This paper describes a technique for obtaining a quantitative assessment of how much improvement is possible in the structure of the visibility parametrization. This is achieved by constructing an alternative visibility diagnostic scheme using a neural network. This statistical model provides a benchmark against which the performance of the current visibility parametrization can be judged, irrespective of the input error. It was found that the neural network achieved significant improvements over the current diagnostic parametrization: a 22% improvement in the geometric mean of the fractional error, and a 15% improvement in the geometric variance of the fractional error. ©Crown Copyright 2008. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.
Meta‐analysis of skewed data: Combining results reported on log‐transformed or raw scales
Authors: Higgins Julian P. T. , White Ian R. , Anzures‐Cabrera Judith 
Published: September 2008

AbstractWhen literature‐based meta‐analyses involve outcomes with skewed distributions, the best available data can sometimes be a mixture of results presented on the raw scale and results presented on the logarithmic scale. We review and develop methods for transforming between these results for two‐group studies, such as clinical trials and prospective or cross‐sectional epidemiological studies. These allow meta‐analyses to be conducted using all studies and on a common scale. The methods can also be used to produce a meta‐analysis of ratios of geometric means when skewed data are reported on the raw scale for every study. We compare three methods, two of which have alternative standard error formulae, in an application and in a series of simulation studies. We conclude that an approach based on a log‐normal assumption for the raw data is reasonably robust to different true distributions; and we provide new standard error approximations for this method. An assumption can be made that the standard deviations in the two groups are equal. This increases precision of the estimates, but if incorrect can lead to very misleading results. Copyright © 2008 John Wiley & Sons, Ltd.
Assignment of pre‐edge peaks in K‐edge x‐ray absorption spectra of 3d transition metal compounds: electric dipole or quadrupole?
Authors: Yamamoto Takashi 
Published: September 2008

AbstractThe characteristics of pre‐edge peaks in K‐edge x‐ray absorption near edge structure (XANES) spectra of 3d transition metals were reviewed from viewpoints of the selection rule, coordination number, number of d‐electrons, and symmetry of the coordination sphere. The contribution of the electric dipole and quadrupole transition to the peaks was discussed on the basis of the group theory, polarized spectra, and theoretical calculations. The pre‐edge peak intensity for Td symmetry is larger than those for Oh symmetry for all 3d elements. The intense pre‐edge peak for tetrahedral species of 3d transition metals is not due to 1s–3d transition, but transition to the p component in d–p hybridized orbital. The mixing of metal 4p orbitals with the 3d orbitals depends strongly on the coordination symmetry, and the possibility is predictable by group theory. The transition of 1s electron to d orbitals is electric quadrupole component in any of the symmetries. The d–p hybridization does not occur with regular octahedral symmetry, and the weak pre‐edge peak consists of 1s–3d electric quadrupole transition. The pre‐edge peak intensity for a compound with a tetrahedral center changes as a function of the number of 3d electrons regardless of the kind of element; it is maximized at d0 and gradually decreases to zero at d10. The features of pre‐edge peaks in K‐edge XANES spectra for 4d elements and the L1‐edge for 5d elements are analogous with those for 3d elements, but the pre‐edge peak is broadened due to the wide natural width of the core level. Copyright © 2008 John Wiley & Sons, Ltd.
Results of a Multimodal Therapy in Patients with Stage IV Barrett’s Adenocarcinoma
Authors: Schauer Matthias , Stein Hubert , Lordick Florian , Feith Marcus , Theisen Joerg , Siewert Joerg Ruediger 
Published: September 2008

AbstractBackgroundLocally advanced and metastatic Barrett’s carcinomas account for the majority of this tumor entity at the time of diagnosis. Many studies have shown that a multimodal therapy concept consisting of neoadjuvant chemotherapy followed by resection can result in improved long‐term survival in patients responding to chemotherapy. The benefit of a multimodal therapy concept in patients with stage IV disease remains unclear.MethodsA total of 178 patients with Barrett’s carcinoma who underwent multimodal therapy with resection of the tumor were reviewed. The pathological staging and the clinical course of patients with metastatic disease, who were treated equally, were compared to patients with locally advanced tumors.ResultsAs expected, postoperative pathological staging showed that patients with metastatic disease have a more advanced T‐ and N‐status. Moreover, the histopathological response according to Becker showed a chemoresistence in 84% of cases with metastatic disease, whereas 54% of patients with locally advanced carcinomas had a good response rate. Overall survival was poor, with 9 months in the metastatic group.ConclusionsThis is the first study to compare the outcome of a modern multimodal therapy concept in patients with metastatic Barrett’s carcinoma in comparison to patients with the locally advanced form of the disease. There are profound differences in the two groups with regard to survival time and response rates. Because of the poor outcome to date, multimodal therapy with resection of the tumor in stage IV disease cannot be recommended.
Information contents misjudged: Digressive convergence to equilibrium in cointegrated prices
Authors: Tswei Keshin , Lai Jing‐yi 
Published: September 2008

AbstractThe spot price on the Taiwan stock index is richer in information than the futures price judged by the price discovery measures of Gonzalo and Granger [Gonzalo, J., & Granger, C.W.J. (1995). Estimation of common long‐memory components in cointegrated systems. Journal of Business and Economic Statistics, 13, 27–35.] and Hasbrouck [Hasbrouck, J. (1995). One security, many markets: Determining the contributions to price discovery. Journal of Finance, 50, 1175–1199.]. What is special about the markets is that both the spot and futures error‐correction coefficients are positive, implying a digressive convergence to their long‐run equilibrium in the error‐correction (EC) process. Innovation accounting suggests that the cause of this digressive equilibrium adjustment is that investors systematically overreact to news in the less informative futures market but under‐react to the more informative spot market. Our contribution is in identifying the digressive convergence implied by same‐sign EC coefficients, comparing it to the normal convergence widely found in opposite‐sign EC models, and providing short‐run mispricing interpretations for both types of convergence to equilibrium.
JACOBI-LIKE FORMS, PSEUDODIFFERENTIAL OPERATORS, AND GROUP COHOMOLOGY
Authors: LEE MIN HO 
Published: September 2008

AbstractPseudodifferential operators are formal Laurent series in the formal inverse ∂−1 of the derivative operator ∂ whose coefficients are holomorphic functions on the Poincaré upper half-plane. Given a discrete subgroup Γ of SL(2,ℝ), automorphic pseudodifferential operators for Γ are pseudodifferential operators that are Γ-invariant, and they are closely linked to Jacobi-like forms and modular forms for Γ. We construct linear maps from the space of automorphic pseudodifferential operators and from the space of Jacobi-like forms for Γ to the cohomology space of the group Γ, and prove that these maps are compatible with the respective Hecke operator actions.
ON SUPERNILPOTENT NONSPECIAL RADICALS
Authors: FRANCE-JACKSON HALINA 
Published: September 2008

AbstractLet ρ be a supernilpotent radical. Let ρ* be the class of all rings A such that either A is a simple ring in ρ or the factor ring A/I is in ρ for every nonzero ideal I of A and every minimal ideal M of A is in ρ. Let $\mathcal {L}\left ( \rho ^{\ast }\right ) $ be the lower radical determined by ρ* and let ρφ denote the upper radical determined by the class of all subdirectly irreducible rings with ρ-semisimple hearts. Le Roux and Heyman proved that $\mathcal {L}\left ( \rho ^{\ast }\right ) $ is a supernilpotent radical with $\rho \subseteq \mathcal {L}\left ( \rho ^{\ast }\right ) \subseteq \rho _{\varphi }$ and they asked whether $\mathcal {L} \left ( \rho ^{\ast }\right ) =\rho _{\varphi }$ if ρ is replaced by β, ℒ , 𝒩 or 𝒥 , where β, ℒ , 𝒩 and 𝒥 denote the Baer, the Levitzki, the Koethe and the Jacobson radical, respectively. In the present paper we will give a negative answer to this question by showing that if ρ is a supernilpotent radical whose semisimple class contains a nonzero nonsimple * -ring without minimal ideals, then $\mathcal {L}\left ( \rho ^{\ast }\right ) $ is a nonspecial radical and consequently $\mathcal {L}\left ( \rho ^{\ast }\right ) \neq \rho _{\varphi }$. We recall that a prime ring A is a * -ring if A/I is in β for every $0\neq I\vartriangleleft A$.
CONTINUITY OF WEIGHTED COMPOSITION OPERATORS BETWEEN WEIGHTED BLOCH TYPE SPACES
Authors: WOLF ELKE 
Published: September 2008

AbstractLet ϕ:D→Dandψ:D→ℂ be analytic maps. These induce a weighted composition operatorψCϕacting between weighted Bloch type spaces. Under some assumptions on the weights we give a necessary as well as a sufficient condition when such an operator is continuous.
Organic block coatings in block-and-ash flow deposits at Merapi Volcano, central Java
Authors: DONOGHUE E. , TROLL V. R. , SCHWARZKOPF L. M. , CLAYTON G. , GOODHUE R. 
Published: September 2008

AbstractThe 1954, 1994, 1998 and 2006 block-and-ash flow deposits from Merapi volcano, Indonesia, contain andesite blocks that display localized, dark surface coatings. These coated blocks are typically found in clusters, but may also occur isolated within the block-and-ash flow deposits. The coatings form irregular patches (tens of centimetres across) on block surfaces, and are characterized by a silver, metallic appearance. The origin and composition of the coatings have not previously been determined, and no comparable deposits have been described in detail from any other volcanically active region of the world. Carbon isotope analyses of coated and uncoated bulk rock material, and of a range of charred and uncharred wood samples, suggest that the dark block coatings at Merapi volcano are organic in origin. Scanning electron microscopy and reflected light microscopy indicate that such coatings may form due to the migration and subsequent deposition of organic carbon in cavities within the andesite blocks. The most recent field evidence from the 2006 block-and-ash flow deposits at Merapi indicates that in situ charcoalification of plant material after block deposition and/or during the final stages of flow, is the major mechanism that forms localized concentrations of block coatings. Isolated coated blocks may result either from recycling of older deposits, or, more likely, from charcoalification and redistribution of plant material caught between colliding lava blocks during flow.