bluuebunny/crossref_metadata_2025 huggingface dataset:
Large plastic stability in magnesium alloys: crystalline vs. amorphous alloys
Authors: Boissière R. , Puech S. , Blandin J.J.
Published: April 2008

Except if strain induces damage, the plastic stability can be roughly estimated thanks to the value of the strain rate sensitivity parameter m. In conventional magnesium alloys, moderate values of m (typically close to 0.3) can be frequently obtained during high temperature deformation. Such values allow reaching significant elongations to fracture. For alloys displaying fine grains, superplastic properties associated with values of m of about 0.5 or more are achievable leading to large elongations to fracture in optimized conditions for which damage processes remain limited. Quite recently, amorphous magnesium alloys have been produced in bulk conditions. In appropriate conditions of deformation, these alloys display Newtonian behaviour (i.e. m = 1). With such rheologies, the plastic stability is expected to be maximal. In this presentation, features in relation with high temperature deformation of amorphous and crystalline magnesium alloys will be compared and apparent similitudes and differences will be discussed.
High resolution surface studies of superplastic deformation in shear and tension
Authors: Rust M.A. , Todd R.I.
Published: April 2008

Despite decades of study, the fundamental mechanisms of superplasticity, particularly relating to the accommodation of grain boundary sliding, are still widely disputed. This is partly due to a lack of information on individual grain deformation and sliding events. Previous studies of superplasticity using surface markers have tended to use either diamond paste scratches, which make quantitative measurements difficult and are open to widely varying interpretation, or regular grids with spacing greater than the grain size, which prevents measurements of intragranular deformation. Recent work has shown that a Focussed Ion Beam (FIB) can be used to create regular, repeating grid marker systems with pitches varying from 0.25 to more than 50 microns. Previously published results in Sn‐Pb have shown the power of this technique, particularly regarding the lack of intragranular deformation and surface grain boundary sliding accommodation mechanisms. The current study has applied the FIB technique to Al5083, a pseudo‐single phase alloy. Tensile tests have been performed with elongations from 5 % to 150 %. Additionally, analogous biaxial shear tests have been performed for comparison and to limit the free surface effects. SEM images of FIB markers before and after deformation have been acquired, and quantitative measurements of the localized strains have been made using 3‐D tilt reconstruction. Shear and tension results show several distinct features. However, no significant intragranular deformation is seen under either set of strain conditions. Possible accommodation mechanisms are discussed.
Titan 6–4 hemispheres for SCA system of ariane 5
Authors: Beck W. , Duong L. , Rogall H.
Published: April 2008

Funded by the European Space Agency (ESA), the Ariane 5 Program has been developed under the responsibility of the CNES, the French Space Agency. Attitude Control of the Ariane 5 Mission is carried out by the SCA (Systeme Controle d'Attitude), developed by Astrium‐Space Transportation (Astrium‐ST). It is the blow down hydrazine system using gaseous nitrogen as pressurant.

The ARIANE 5 ‐SCA Tank ‐ Fig.1 ‐ is manufactured from TiAl6V4‐hemispheres essentially performed via Super Plastic Forming (SPF) process. The tank shell wall thickness achieved need not to be mechanically reworked except small domains prepared for welding. Vis‐à‐vis the common tank production which employs hemispheres resulted by mechanical milling out of forged shell, the SPF provides certainly saving on milling efforts as well as significant reduction on material wasting. Also shown that is for tank component submitted to space application, the SPF as production method commonly undergoes development and verification efforts in engineering elaborating focused on Test‐shell, Qualification‐shell and such which provides samples for material strength and technological verifications. Enclosing is also a brief overall display addressing successful use of SPF‐shell in producing tanks for the space flight today. Up to now more then 100 Tanks have been manufactured by Astrium‐ST and > 90 Tanks were successful used in Ariane 5 launchers with various missions.
Design, production and testing of a titanium exhaust duct for noise and weight reduction
Authors: Beck W. , Chaniot D. , Larrouy T. , Marcel Y. , Yannovitch P.
Published: April 2008

Helicopter exhausts are usually basic components not yet developed to achieve the best noise reduction performance. This needs to change to continue complying with ever more restrictive noise regulations. A more efficient acoustic design could be reached using a complex configuration with assembly of multiple walls and 3D optimized geometry. As the exhausts nozzle are usually built out of Ni based alloys, the weight of such a component would increase. Such an increase could have a negative effect on the payload of the aircraft. Due to high temperatures and pressures of gas stream, Cp Titanium is limited for this application but heat resistant titanium alloys such as Beta21S and Ti 6–2‐4–2 would be a good substitution material as it provides significant weight reduction and capacity to sustain further power increase of the Helicopter engines. An European Project named “HORTIA” was funded to demonstrate the feasibility of using Heat and Oxidation Resistant Titanium Alloys for exhaust ducts in a noise and weight reduction objective. Studies were conducted on these materials to evaluate their mechanical performances and resistance against corrosion at high temperature for a service application. A thermo‐mechanical simulation of stress and temperature fields validated the definition design of a new component in an acoustically efficient configuration. An analysis of forming and welding parameters led to the industrial manufacturing of a complete exhaust with techniques like Super‐Plastic Forming and Laser Beam Welding. Finally the nozzle was successfully tested on en engine test bed for endurance and acoustic performance.
Finite element based predictions of life limiting behaviour for a large SPF tool
Authors: Deshpande A.A. , Leen S.B. , Hyde T.H.
Published: April 2008

SPF tool distortion due to the thermal cycling can lead to the forming of faulty SPF parts. In addition, thermo‐mechanical fatigue and creep can cause cracking, which eventually lead to un‐repairable damage to the tool. The aim of this paper is to investigate the thermo‐mechanical distortion behaviour of a representative large SPF tool under realistic forming conditions using finite element analysis. Platen‐tool contact and clamping pressure along the edges of the tool during the dwell time are modelled. The effects of heating and cooling cycles on tool distortion are analysed using different thermal histories with different heating and cooling rates. The effect of batch size on tool distortion is evaluated to optimise the batch size.
Increasing stable deformation by declining temperature during the process
Authors: Ziegelheim J. , Ohsawa H. , Motegi H. , Koiwai K.
Published: April 2008

Recently increasing amount of light metal sheets, especially based on magnesium, is being involved into various structural constructions and functional components. Such a rising trend can be observed, for instance, at automotive, aerospace and electronic industry. On the other hand there exist some processing difficulties, such as forming limits, caused by crystalline structure.

To make processing of magnesium materials most reasonable with a maximum economical and material’s effect, detailed investigation of the material’s mechanical behavior is necessary to realize. Especially, an use of superplasticity is a point of the main interest.

By optimum settings of the deformation process (especially temperature and strain rate) the superplastic conditions were determined optimally. Moreover, it was discovered that variable temperature very positively affects the superplasticity of magnesium materials. Actually by changing temperature conditions during the deformation, even higher level of superplastic deformation without rupture can be obtained. This very interesting fact was observed at the elevated temperatures that decrease almost constantly during the deformation process.

Thus previously widely used constant temperature treatment opens door to the dynamic problems of searching for the optimal temperature gradient and its variation.
The manufacture of superplastic Magnesium alloy sheet
Authors: Grimes R. , Jackson M. , Moorhouse B. , Dashwood R.
Published: April 2008

Probably because of their propensity to dynamically recrystallise, superplastic behaviour can be obtained from magnesium alloys considerably more easily than from comparable aluminium alloys. In some cases even as cast magnesium alloys can exhibit reasonable superplasticity and there appears no need for the special alloying additions or complex thermal mechanical treatments required by aluminium alloys such as AA2004 or AA7475. The paper describes the superplastic behaviour (in uniaxial tension) and microstructure of sheet processed from strip cast AZ31 and AZ91. The material was tested in the as‐cast condition and after warm rolling to a number of gauges. Industrially useful superplastic capability was demonstrated in strip cast AZ31 and AZ91 in the as cast condition. Furthermore good superplastic capability was also demonstrated in sheet rolled from the cast metal and the ductilities obtained were not significantly influenced by rolling strain. Twin roll strip casting represents a feasible and simple route for the production of superplastic material either for use in the as cast condition or after rolling to the required gauge.
Superplastic forming of friction stir welds in Titanium alloy 6Al‐4V: preliminary results
Authors: Sanders D.G. , Ramulu M. , Edwards P.D.
Published: April 2008

The trend in design and fabrication of aerospace structure is moving rapidly towards the use of composite materials and the consolidation of many pieces into large monolithic assemblies. Titanium alloy 6Al‐4V is more compatible with composite materials than aluminum alloys because of its superior corrosion resistance and closer match to the coefficient of thermal expansion. In addition, many components that are used for the newer composite based aircraft, and are subjected to high service temperatures, are fabricated from titanium using Superplastic Forming (SPF) and Diffusion Bonding (SPF/DB). However, the use of SPF titanium parts has been limited up until now due the size restriction of standard sheets from the titanium mills, which is generally available at a maximum size of 1.2 m x 3.6 m. The purpose of this study was to develop the Friction Stir Welding (FSW) process for both standard and fine grain titanium alloy 6Al‐4V in a bid to find a process that would allow the joining of multiple pieces to fabricate much larger components. Further, the FSW process was refined such that the welds were made to have superplastic properties equal to those of the parent sheet. A secondary goal of this effort was to build full size SPF prototype parts of a generic jet engine nacelle Lipskin using one FSW titanium blank. SPF of 7475 aluminum had been reported previously in the literature by Mahoney, Barnes, Mishra and others. During this study, the FSW process for 5083 Superplastic grade aluminum was developed simultaneously along with titanium 6Al‐4V. The aluminum material was used to reduce the cost of developing the SPF manufacturing process to fabricate full scale engine inlet test components. FSW blanks of both materials were used for the initial forming trials.
Enhanced superplastic deformation behavior of ultrafine‐grained Ti‐6Al‐4V alloy
Authors: Saitova L. , Semenova I. , Höppel H.W. , Valiev R. , Göken M.
Published: April 2008

The mechanical behavior of the Ti‐6Al‐4V ELI alloy in both conventional grain size (CG) and ultrafine‐grained (UFG) conditions under tension and compression at elevated temperatures (500–800 °C) is considered. Grain refinement by equal‐channel angular pressing (ECAP) followed by multicycle extrusion was observed to result in a considerable improvement of superplastic characteristics of Ti‐6Al‐4V ELI alloy. The alloy exhibits a superplastic deformation behavior already at 600 °C. The enhanced regime of superplasticity allows more efficient forming of parts and components. In addition, the UFG microstructure and, consequently, enhanced mechanical properties are kept after superplastic forming.
Gas‐Phase Olefin Polymerization in the Presence of Supported and Self‐Supported Ziegler‐Natta Catalysts
Authors: Kanellopoulos Vassileios , Gustafsson Bill , Kiparissides Costas
Published: April 2008

The RPPFM is employed to describe the gas‐phase catalytic polymerization of ethylene in the presence of supported or self‐supported Z‐N catalysts. Numerical simulations are carried out to analyze the effect of the catalyst type on the polymerization rate, particle overheating and the average molecular polymer properties of the polyolefin. It is shown that non‐porous, self‐supported Ziegler‐Natta catalysts exhibit higher particle growth rates and lower particle overheating. The average molecular weight of polyethylene produced by both catalysts is almost identical. Depending on particle size and polymer crystallinity, the average monomer solubility and the effective monomer diffusivity can significantly vary.

magnified image
Competitive heavy metal removal by poly(2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid‐co‐itaconic acid)
Authors: Çavuş Selva , Gürdağ Gülten
Published: April 2008

The competitive removal of Pb2+, Cu2+, and Cd2+ ions from aqueous solutions by the copolymer of 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid (AMPS) and itaconic acid (IA), P(AMPS‐co‐IA), was investigated. Homopolymer of AMPS (PAMPS) was also used to remove these ions from their aqueous solution. In the preparation of AMPS–IA copolymer, the molar percentages of AMPS and IA were 80 and 20, respectively. In order to observe the changes in the structures of polymers due to metal adsorption, FTIR spectra by attenuated total reflectancetechnique and scanning electron microscopy (SEM) pictures of the polymers were taken both before and after adsorption experiments. Total metal ion removal capacities of PAMPS and P(AMPS‐co‐IA) were 1.685 and 1.722 mmol Me2+/gpolymer, respectively. Experimental data were evaluated to determine the kinetic characteristics of the adsorption process. Competitive adsorption of Pb2+, Cu2+, and Cd2+ ions onto both PAMPS and P(AMPS‐co‐IA) was found to fit pseudo‐second‐order type kinetics. In addition, the removal orders in the competitive adsorption of these metal ions onto PAMPS and P(AMPS‐co‐IA) were found to be Cd2+ > Pb2+ > Cu2+ and Pb2+ > Cd2+ > Cu2+, respectively. Copyright © 2008 John Wiley & Sons, Ltd.
Flammability properties of intumescent PLA including starch and lignin
Authors: Réti C. , Casetta M. , Duquesne S. , Bourbigot S. , Delobel R.
Published: April 2008

The aim of this study is to evaluate the efficiency of different intumescent formulations to flame retard polylactic acid (PLA). First, the ammonium polyphosphate (APP)/pentaerythritol (PER) system is chosen because it previously demonstrated a good behavior for polyethylenic matrices. The PER is then substituted by bioresources such as lignin and starch. The flame retardant properties of the various formulations are evaluated by limiting oxygen index (LOI), UL‐94, and cone calorimetry. Compared to the PLA/APP/PER composite, the materials containing lignin and starch show lower LOI values but still commercially acceptable (superior to 32%). In contrast, the UL ratings obtained for these formulations are superior to that containing PER (V0 against V2 rating).

The cone calorimeter analysis confirms the formation of an intumescent structure for the “green” composites, with a final residue corresponding to 50% of the initial sample mass and also a decrease in the peak of heat release of 50%. Finally, the composition of the formulation is optimized following a mixture design methodology to maximize the quantity of bioresources. A 32% LOI value is obtained for a composite containing 60% PLA, 12% APP, and 28% starch. Copyright © 2008 John Wiley & Sons, Ltd.
Influence of alcohol pre‐infusion on the quality of VARTM composites
Authors: Qiu Jingjing , Li Jing , Zhang Chuck , Liang Richard , Lin Shui‐Shun , Wang Ben , Walsh Shawn
Published: April 2008

In the vacuum assisted resin transfer molding (VARTM) process, part‐to‐part variations such as the uncertainty in the permeability and race tracking phenomenon make it difficult to achieve consistent mold filling and ensure part quality of composites. Alcohol pre‐infusion was presented in this study as a novel real‐time monitoring and control approach for the flow process in the VARTM process, alcohol test fluid is infused before the actual resin infusion to locate the potential dry spots without using the large quantity of sensors. Then corresponding process control strategy is designed, such as opening the auxiliary gate at specific moment on those predicted dry spot locations to compensate flow defects. Moreover, alcohol can be easily removed by heat without changing the local permeability. The influence of alcohol pre‐infusion on the quality of VARTM composites were investigated in this study. The mechanical tests were conducted to verify that the alcohol pre‐infusion approach has no significant effect on composite properties because alcohol can be removed from fiber by heat and air flow. Specifically, DMA, TGA, and FTIR spectrum proved that negligible difference existed on the resin–fiber interface between the composites with or without alcohol pre‐infusion. Finally, the microscopy results revealed a similar failure path in a resin matrix. TMA results also demonstrated similar dimension stability. This alcohol pre‐infusion approach was effective when compared with computer simulation and could eliminate the occurrence of dry spots and voids without using sensors or data‐acquisition system. The control schemes were shown in a case study to be capable of compensating the flow defects and achieving desired fill patterns in the face of permeability uncertainty. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Chronic statin therapy and the risk of colorectal cancer
Authors: Yang Yu‐Xiao , Hennessy Sean , Propert Kathleen , Hwang Wei‐Ting , Sarkar Monika , Lewis James D.
Published: April 2008

Background and Aims

Epidemiologic studies on a potential chemopreventive effect of statin therapy have yielded conflicting results. We sought to clarify whether long‐term statin therapy has a chemopreventive effect on the risk of colorectal cancer (CRC) in a large, population‐representative cohort.

Methods

A nested case–control study was conducted among patients ≥50 years of age and with ≥5 years of CRC‐free initial follow‐up in the General Practice Research Database (GPRD; 1987–2002). Cases consisted of all patients with incident CRC. Up to 10 controls were matched with each case on practice site and both duration and calendar time of follow‐up prior to the index date. The primary exposure of interest was ≥5 years of cumulative statin use.

Results

We identified 4432 incident CRC cases and 44 292 controls. The adjusted odds ratio (OR) for ≥5 years of statin exposure was 1.1 (95% confidence interval (CI): 0.5–2.2). Chronic NSAID/aspirin use did not modify this primary association (test for interaction, p = 0.5). Compared to statin non‐users, the adjusted OR for 10 years of statin exposure was 1.3 (95% CI: 0.6–2.7), and the adjusted OR associated with the highest quartile of cumulative statin dose was 1.2 (95% CI: 0.9–1.7). There was a non‐statistically significant trend towards a possible reduction in CRC risk among users of high daily statin dose.

Conclusion

Long‐term statin therapy at usual doses was not associated with a significantly reduced risk of CRC. A chemopreventive effect at high daily doses cannot be excluded. Copyright © 2008 John Wiley & Sons, Ltd.
Grafting of Paper by Silane Coupling Agents Using Cold‐Plasma Discharges
Authors: Gaiolas Carla , Costa Ana Paula , Nunes Mario , Silva Manuel José Santos , Belgacem Mohamed Naceur
Published: April 2008

The treatment of cellulose with cold plasma in the presence of two silanes is found to be efficient in the grafting of cellulose macromolecules. The occurrence of the grafting is proven by contact angle measurement, ESCA, and SEM. Thus, after plasma treatment the polar component of the surface energy of the treated samples decreases from 23 mJ · m−2 to practically zero. The ESCA spectra showed the appearance of two new peaks at 102 and 150 eV, relative to the presence of Si atoms and a substantial increase in Cl signal, attributed to the enrichment of the surface by CH moieties borne by the silanes. SEM confirms the presence of the silane, both in the bulk and at the surface of the treated samples.

magnified image
Resistance monitoring in codling moth: a need for standardization
Authors: Reyes Maritza , Sauphanor Benoît
Published: April 2008

BACKGROUND: A wide range of methods has been used for monitoring resistance in Cydia pomonella L. However, the results from specific tests are not always concordant and they generate doubts over the extent to which the data represent the field situation. Therefore, the variability in the expression of resistance mechanisms and in resistance ratios between developmental stages and their reliability in a field situation were studied.

RESULTS: Neonate larvae showed the highest insecticide resistance, except to spinosad. Resistance ratios were from 2 to 9.5, depending on the insecticide and the strain tested, when compared with the susceptible strain. Spinosad exhibited the highest resistance ratio for diapausing larvae (4.4, 12.2 and 4.4 for Raz, Rdfb and RΔ strains, respectively). Enzymatic ratios were higher in adults than in neonates or diapausing larvae, and the highest enzymatic ratios were observed for mixed‐function oxidases (7.3–36.7 for adults of resistant strains).

CONCLUSIONS: The sensitivity of different instars depends on the insecticides used, and there is a differential expression of resistance mechanisms between stages. For the population considered in this study, tests on neonates provided the most consistent results to the field situation, but adult response to chlorpyrifos‐ethyl and azinphos‐methyl in the laboratory was also consistent with the field results. Copyright © 2008 Society of Chemical Industry
Using alternative data sources to study rural migration: examples from Illinois
Authors: Foulkes Matthew , Newbold K. Bruce
Published: April 2008

One of the problems frequently faced by migration researchers is the paucity of national census migration data for small rural areas. Drawing upon a larger, multi‐level research project that focused upon rural poverty migration within Illinois, this article illustrates the opportunities and challenges associated with using community‐based data sources to measure mobility in small rural communities. Use of alternative migration data sources can present opportunities to circumvent common problems with census‐based data sources, including addressing temporal shortfalls, providing custom geographies, and capturing the movement of difficult‐to‐enumerate subpopulations. Alternative data‐sets may also allow researchers to formulate new questions that are more oriented to society's pressing problems. Yet, users of non‐traditional data‐sets also face issues of indirect measurement, data quality, comparability, replication, costs, and moral and ethical concerns. As use of non‐traditional migration data sources increases, researchers will need to become familiar with both the benefits and pitfalls of these data‐sets. Copyright © 2008 John Wiley & Sons, Ltd.
X‐ray diffraction studies of selective area grown InGaN/GaN multiple quantum wells on multi‐facet GaN ridges
Authors: O'Malley S. M. , Bonanno P. L. , Wunderer T. , Brückner P. , Neubert B. , Scholz F. , Kazimirov A. , Sirenko A. A.
Published: April 2008

The structural properties of InGaN/GaN multiple quantum wells (MQW) were studied using synchrotron based high resolution x‐ray diffraction (HRXRD). MQW structures were grown on the top and sidewall facets of triangular and trapezoidal shaped GaN ridges by metalorganic vapour phase epitaxy (MOVPE) in the regime of selective area growth (SAG). Period and strain variations as a function of oxide mask width were determined for both the sidewall and the top facet growth. Oxide mask widths ranged between 2 and 20 µm with openings between adjacent masks of 4 and 6 µm. Analysis of the x‐ray diffraction curves revealed a sidewall / vertical growth rate ratio of ∼0.3 through a comparison of the top to sidewall facet MQW periods. Masks orientated along the 〈11‐20〉 crystallographic direction showed stronger growth enhancement along with large global strain for MQW growth on the top (0001) plane. Interpreting our results within the framework of vapour phase diffusion revealed that inter‐facet migration of group‐III species needs to be taken into account. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Enhancement of external quantum efficiency in GaN‐based light emitting diodes using a suspended geometry
Authors: Fellows Natalie , Masui Hisashi , Sato Hitoshi , Asamizu Hirokuni , Iza Michael , Zhong Hong , Nakamura Shuji , DenBaars Steven P.
Published: April 2008

Using a transparent and mirror‐less chip mounting technique we have increased the total external efficiency by 26%. This increase in the external quantum efficiency for a light‐emitting diode (LED) was based on c ‐plane (0001) bulk GaN employing a suspended geometry. A small size LED (200 x 550 μm2) affixed to a Ag header is compared to an LED die lifted off the header. The output power for the LED in the suspended geometry was 30.4 mW, a 13% increase over the conventional placement and the EQE increased from 49% to 56% at a forward current of 20 mA under pulsed conditions. The suspended die was then placed into a cone optic and its output power and EQE improved to 34 mW and 62%, respectively. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High quality, high efficiency and ultrahigh In‐content InGaN QWs – the problem of thermal stability
Authors: Fuhrmann D. , Jönen H. , Hoffmann L. , Bremers H. , Rossow U. , Hangleiter A.
Published: April 2008

InxGa1‐xN/GaN quantum well (QW) structures with Indium concentrations above 30% suited for light emitters in the green and beyond have been investigated. The structures were optimized for homogeneous Indium distributions and abrupt interfaces. We obtained very high internal quantum efficiencies (IQE) of 80% and 70% for 460 nm and 510 nm emission wavelength, respectively. However, for high In concentrations the heterostructures are thermally less stable. This is evident from systematic studies including varied GaN cap temperatures and different post annealing procedures. For elevated temperatures we observe a reduction of the PL intensity, a broadening and a shift to higher energies of the PL lines without indication of phase separation. The reason is the soft indium‐nitrogen bond, the degradation likely occurs by In interdiffusion or outdiffusion via defects in the structures. The critical temperatures are well below those typical for p‐GaN contact layer growth and thus need to be considered in device applications. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
GaN growth on silane exposed AlN seed layers
Authors: Ruiz‐Zepeda F. , Contreras O. , Dadgar A. , Krost A.
Published: April 2008

The microstructure and surface morphology of GaN films grown on AlN seed layers exposed to silane flow has been studied by TEM and AFM. The epilayers were grown on silicon (111) substrates by MOCVD. The AlN seed layer surface was treated at different SiH4 exposure times prior to the growth of the GaN film. A reduction in the density of threading dislocations is observed in the GaN films and their surface roughness is minimized for an optimal SiH4 exposure time between 75‐90 sec. At this optimal condition a step‐flow growth mode of GaN film is predominant. The improvement of the surface and structure quality of the epilayers is observed to be related to an annihilation process of threading dislocations done by SiNx masking. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of Mg‐doped AlInN grown by metalorganic vapor phase epitaxy
Authors: Cheng A. T. , Su Y. K. , Lai W. C.
Published: April 2008

We report on the growth of undoped and Mg‐doped AlInN by metalorganic vapor phase epitaxy (MOVPE). The indium content and the full width at half maximum (FWHM) of undoped AlInN layer were 20.9% and 219.6 arcsec, respectively, from HRXRD measurement. It was also observed that an additional satellite peak was formed near the AlInN peak after introducing the Mg dopant. The sheet hole concentration of 4.73×1012 cm–2 was achieved after performing the thermal annealing. As the flow rate of Cp2Mg source was increased, we found that both the satellite peak and the AlInN peak shifted toward higher angles. However, higher Cp2Mg flow rate would not only decrease the conductivity of AlInN layer due to the higher Al content shown in HRXRD spectrum but increase the surface roughness. Therefore, these results suggest that p‐type AlInN cladding layer nearly lattice‐matched to GaN will be realized with lower Cp2Mg flow rate for optical device applications. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
MOVPE growth and photoluminescence properties of InAsN QDs
Authors: Kuboya S. , Takahashi S. , Thieu Q. T. , Nakajima F. , Katayama R. , Onabe K.
Published: April 2008

The self‐assembled InAsN quantum dots (QDs) were grown on the GaAs (001) substrates by MOVPE using 1,1‐dimethylhydrazine (DMHy) as the N precursor, and their photoluminescence (PL) properties were investigated. The N incorporation leads to a decrease in the QDs size for an equivalent amount of source supply due to the increase in the wetting layer thickness. It also leads to an increase in the QDs density which is interpreted by the reduced surface migration length. The PL from the electron ground state of the InAsN QDs clearly shows the red‐shift to 1159 nm by the N incorporation, indicating that the effect of the huge bandgap bowing is dominant over the quantum size effect in the InAsN QDs. The thermal activation energy of the QDs derived from the temperature dependence of the integrated PL intensity decreases from 176 meV to 140 meV by the DMHy supply, which is explained by the lowering of the electron quantum state of the thicker wetting layer caused by the N incorporation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Increase in the growth rate of GaN single crystals grown by gallium hydride vapor phase epitaxy method
Authors: Imade Mamoru , Yamada Norihide , Kitano Yoshihiro , Kawamura Fumio , Yoshimura Masashi , Kitaoka Yasuo , Mori Yusuke , Sasaki Takatomo
Published: April 2008

A dependence of Gallium hydride (GaHx: x = 1, 2, 3) production on the growth rate of GaN crystals grown by the gallium hydride vapor phase epitaxy (GaH‐VPE) method was investigated. By this method, GaN crystals are synthesized in a reaction between GaHx and NH3. The growth rate of GaN crystals has been as low as 20 μm/h at a maximum because the poor reactivity of H2 gas with Ga metal limits the production of GaHx. In this study, the interfacial area between Ga metal and H2 gas was enlarged to increase the GaHx synthesis, which thereby enabled an increase in the growth rate to 68 μm/h. We showed clearly that the growth rate of GaN by the GaH‐VPE method is limited by the efficiency of the reaction between the Ga metal and H2 gas. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
V‐defect analysis in green and deep green light emitting diode structures
Authors: Zhu M. , Detchprohm T. , You S. , Wang Y. , Xia Y. , Zhao W. , Li Y. , Senawiratne J. , Zhang Z. , Wetzel C.
Published: April 2008

In 535‐565 nm green and deep green LED dies on c‐plane sapphire, we correlate the structural morphology with photoluminescence performance. Two classes of material with active region roughness of 4 nm and 0.4 nm (RMS) are analyzed in transmission electron microscopy. In the rough material, a high density of edge‐type dislocations is identified that originates within the quantum wells (QWs). They initiate V‐defects that exhibit {10$ \bar 1 $1} growth facets with a second set of narrow QWs and barriers. As V‐defects widen with progressive growth, the width of QW and barriers on the c‐plane increases. In the smooth material, however, no V‐defects can be found. QWs and barriers are highly uniform and homogenous throughout the structure. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ultra‐incompressible and hard technetium carbide and rhenium carbide: First‐principles prediction
Authors: Wang Yuan Xu
Published: April 2008

Using density functional theory, the author predicts that the compounds ReC and TcC with the hexagonal WC‐like structure are ultra‐incompressible and hard materials. This is concluded from the very large bulk and shear moduli. The phonon dispersion reveals no soft modes indicating the stability of the two materials. The calculated density of states shows that ReC and TcC are metallic. The structural and elastic properties of OsC, IrC, and PtC with hexagonal and cubic structure are also investigated for comparison. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The effect of temperature and humidity fluctuations on the liquid water path of non‐precipitating closed‐cell stratocumulus clouds
Authors: de Roode Stephan R. , Los Alexander
Published: April 2008

The spatial variability of the liquid water path (LWP) is analyzed from a large‐eddy simulation of the diurnal cycle of stratocumulus clouds as observed during FIRE I. In stratocumulus clouds, the temperature and the total specific humidity cannot fluctuate independently, but are tightly connected to fluctuations in the liquid water potential temperature. If the latter are relatively small, a strong positive correlation between the temperature and the total specific humidity can be expected. The effect of temperature fluctuations on the magnitude of liquid water fluctuations must be considered to properly compute the LWP distribution in stratocumulus clouds.

The simulated stratocumulus cloud fields are used to compute the albedo inhomogeneity factor χ according to the effective thickness approach. During the day, the mean LWP decreases due to short‐wave radiative warming. Also, the probability density function for the LWP becomes positively skewed due to cumuli that have their base well below the mean stratocumulus cloud‐base height. For this situation, the inhomogeneity factor χ displays a minimum value of about 0.85. For solid (unbroken) cloud with an assumed Gaussian distribution for the optical depth, we find that the minimum inhomogeneity factor will be about 0.8. This minimum value for the inhomogeneity factor, and that from the LES results, are larger than reported from FIRE I observations. Copyright © 2008 Royal Meteorological Society
Regional channel geometry equations: a statistical comparison for physiographic provinces in the eastern US
Authors: Johnson P. A. , Fecko B. J.
Published: April 2008

Regional stream channel equations are created to solve for a specified discharge or channel dimensions as a function of drainage area. In recent years, regional equations have been developed by the US Geological Survey (USGS) and US Fish and Wildlife Service (USFW), as well as various state agencies for use in the preliminary design of stable channels. The regional equations are created using measured stable channel dimensions. Physiographic provinces have been used as boundaries for the development of these equations due to the perceived roles of climate, geology and physiography in shaping channels. Data collection within each physiographic province has typically been confined to a study area which encompasses parts of one or more states, but not the whole physiographic province. Thus, the use of the equations is restricted to the physiographic province(s) and the state(s) for which they have been developed. The purpose of this study was to determine whether the regional equations are statistically different within a single physiographic province and different between physiographic provinces. The results of the statistical analyses of the regional equations and their associated data showed that the majority of the equations are similar within their respective physiographic provinces. Testing between provinces showed that the Appalachian Plateau, New England and Valley and Ridge provinces have statistically similar equations. Based on the evidence presented in this study, separating regional equations by physiographic regional boundaries is valid. New equations for those data that showed statistical similarity were developed. Copyright © 2008 John Wiley & Sons, Ltd.
Multivariate statistical analysis of non‐mass‐selected ToF‐SIMS data
Authors: Smentkowski V. S. , Ostrowski S. G. , Kollmer F. , Schnieders A. , Keenan M. R. , Ohlhausen J. A. , Kotula P. G.
Published: April 2008

Cluster LMIGs are now regarded as the standard primary ion guns on time‐of‐flight secondary ion mass spectrometers (ToF‐SIMS). The ToF‐SIMS analyst typically selects a bombarding species (cluster size and charge) to be used for material analysis. Using standard data collection protocols where the analyst uses only a single primary bombarding species, only a fraction of the ion‐beam current generated by the LMIG is used. In this work, we demonstrate for the first time that it is possible to perform ToF‐SIMS analysis when all of the primary ion intensity (clusters) are used; we refer to this new data analysis mode as non‐mass‐selected (NMS) analysis. Since each of the bombarding species has a different mass‐to‐charge ratio, they strike the sample at different times, and as a result, each of the bombarding species generates a spectrum. The resulting NMS ToF‐SIMS spectrum contains contributions from each of the bombarding species that are shifted in time. NMS spectra are incredibly complicated and would be difficult, if not impossible, to analyze using univariate methodology. We will demonstrate that automated multivariate statistical analysis (MVSA) tools are capable of rapidly converting the complicated NMS data sets into a handful of chemical components (represented by both spectra and images) that are easier to interpret since each component spectrum represents a unique and simpler chemistry. Copyright © 2008 John Wiley & Sons, Ltd.
The new Latin American landscape
Authors: Marcovitch Jacques
Published: April 2008

For decades, Latin America has been accumulating a social liability of considerable proportions. Precariousness in education and health, food insecurity in a large stratum below the poverty line, violence, unemployment, and unlawfulness sharpen the incorrigible skepticism of opinion makers. Nevertheless, Latin America is an immense territory of possibilities to be exploited with independence, pragmatism, and proper vision of the future. The most promising news is that the region as a whole, despite insufficient progress in the smallest and poorest countries, is very close to meeting the targets in the fight against hunger. The greatest regional challenge is to harmonize economic expansion and the social profit that it represents. © 2008 Wiley Periodicals, Inc.
Changes in body composition during weight loss in obese client-owned cats: Loss of lean tissue mass correlates with overall percentage of weight lost
Authors: German Alexander J. , Holden Shelley , Bissot Thomas , Morris Penelope J. , Biourge Vincent
Published: April 2008

Obesity is one of the most common medical diseases in cats, but there remains little information on success of weight loss regimes in obese client-owned cats. No information currently exists on body composition changes during weight loss in clinical cases. Twelve obese client-owned cats undertook a weight loss programme incorporating a high-protein low fat diet. Body composition was quantified by dual-energy X-ray absorptiometry, before and after weight loss. Mean (±standard deviation) weight loss was 27±6.8% of starting weight, and mean rate of weight loss was 0.8±0.32% per week. Mean energy allocation during weight loss was 32±7.0 kcal/kg target weight. Mean composition of tissue lost was 86:13:1 (fat:lean:bone mineral). The proportion of lean tissue loss was positively associated with overall percentage of weight loss (simple linear regression, r2=44.2%, P=0.026). Conventional weight loss programmes produce safe weight loss, but lean tissue loss is an inevitable consequence in cats that lose significant proportions of their starting body weight.
Monte Carlo simulation in a strongly coupled linear chain
Authors: BEKDA A. , DJEBLI M. , BELDJOUDI N.
Published: April 2008

Monte Carlo simulation is conducted for a strongly coupled one-dimensional confined-particles system. We deal with an infinite chain of positively charged dust particles. The particles interact through the Yukawa screened potential. It is found that a critical value exists for the number of closest neighbors that are involved in the interaction. The inter-particle distance at equilibrium is found. Using these results, we study the dust-acoustic as well as the dust-lattice modes for two situations. In the first we neglect the friction force while in the second situation the presence of an ambient gas in plasma is considered.
Numerical prediction of the saturation limit of atmospheric pressure AC dielectric barrier discharges
Authors: ARSHAK KHALIL , GUINEY IVOR , FORDE EDWARD
Published: April 2008

In this paper the evolution of species densities up to the saturation limit in pulsed dielectric barrier discharges in atmospheric air plasma is predicted. The saturation limit itself is presented in the form of an exponential equation and is validated by computer modeling of continuity equations and atmospheric reactions coupled with appropriate dielectric dependent boundary conditions. Microdischarge streamer times are treated independently and a profile of the species generation due to all microdischarges within the plasma is presented. Quasi-neutrality is assumed for calculations and a theoretical maximum value for species densities in such a plasma is additionally outlined. Results show a good agreement between simulated and calculated values and serve to illustrate the onset of saturation in atmospheric pressure plasmas in general. Practical conditions of voltage, gap distance and frequency are incorporated so as to make the model as realistic as possible.
Innate immune response mechanisms in the intestinal epithelium: potential roles for mast cells and goblet cells in the expulsion of adultTrichinella spiralis
Authors: KNIGHT P. A. , BROWN J. K. , PEMBERTON A. D.
Published: April 2008

Gastrointestinal infection with the nematodeTrichinella spiralisis accompanied by a rapid and reversible expansion of the mucosal mast cell and goblet cell populations in the intestinal epithelium, which is associated with the release of their mediators into the gut lumen. Both goblet cell and mast cell hyperplasia are highly dependent on mucosal T-cells and augmented by the cytokines IL-4 and IL-13. However, the contribution of both mast and goblet cells, and the mediators they produce, to the expulsion of the adults ofT. spiralisis only beginning to be elucidated through studies predominantly employingT. spiralis-mouse models. In the present article, we review the factors proposed to controlT. spiralis-induced mucosal mast cell (MMC) and goblet cell differentiation in the small intestine, and focus on some key MMC and goblet cell effector molecules which may contribute to the expulsion of adult worms and/or inhibition of larval development.
Aesthetic christology and medical ethics: the status of Christ's gaze in care for the suffering
Authors: Tolley David C.
Published: April 2008

This article seeks to offer an alternative to traditional understandings of how doctrine can inform the ways that medical professionals and others care for people who suffer. Placing traditional christological reflections in conversation with an aesthetically generated christology, I consider how the beauty of encounter can shape us. First, I consider how encounters in general can shape us, and then I reflect in particular upon how encounters with Christ, as construed by Hans Urs Von Balthasar, can shape us. I suggest that personal encounters shape us by forcing us to cross stories with others and by affecting us at the level of personal desire. Then, I articulate how an encounter with Christ – especially with Christ's questioning, liberating gaze as described by Von Balthasar – can motivate people to approach others with this same gaze. Lastly, I focus upon how caregivers can embody Christ's gaze at the bedside in acknowledgement, intimacy, communion and respectful silence with those who suffer.
Grammaticality judgments in children: The role of age, working memory and phonological ability
Authors: McDONALD JANET L.
Published: April 2008

This paper examines the role of age, working memory span and phonological ability in the mastery of ten different grammatical constructions. Six- through eleven-year-old children (n=68) and adults (n=19) performed a grammaticality judgment task as well as tests of working memory capacity and receptive phonological ability. Children showed early mastery of some grammatical structures (e.g. word order, article omissions) while even the oldest children differed from adults on others (e.g. past tense, third person singular agreement). Working memory capacity and phonological ability accounted for variance in grammaticality judgments above and beyond age effects. In particular, working memory capacity correlated with structures involving verb morphology and word order; phonological ability was important for structures with low phonetic substance. Children's relative difficulty with the different constructions showed parallels to adult performance under memory load stress, indicating working memory capacity may be a limiting factor in their performance. Implications for performance by memory and phonologically impaired populations are discussed.
The representation of morphologically complex words in the developing lexicon*
Authors: RABIN JENNIFER , DEACON HÉLÈNE
Published: April 2008

The study reported here examined the manner in which children represent morphologically complex words in the lexicon. Children in grades 1 to 5 completed a fragment completion task to assess the priming effects of morphologically related words. Both inflected and derived words (e.g. needs and needy, respectively) were more effective primes than control words (e.g. needle) that share similar orthography and phonology with the target word (e.g. need). These effects were consistent across the developmental period studied. Further, equivalent priming effects from the inflected and derived forms suggest that these word types are represented similarly in the developing lexicon.
Instruments of Faith and Unity in Canon Law: The Church of Nigeria Constitutional Revision of 2005
Authors: Kuehn Evan F
Published: April 2008

The Church of Nigeria's canon law revision of 14 September 2005 redefined the terms of inter-provincial Anglican unity from a focus on communion with the Archbishop of Canterbury to communion based explicitly upon the authority of scripture and historic doctrinal statements. This paper will examine the revision as an ecclesiastical reform connected to, yet independent from, the current controversy over human sexuality. Pertinent issues of episcope and ecclesial communion as they are affected by the canon law change will then be examined. Finally, the ecumenical implications of the revision will be discussed, with particular reference to the Anglican–Roman Catholic dialogue and the ‘continuing’ churches of North America.