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Kmetijstvo je vrsta dejavnosti, ki je zelo odvisna od vremenskih in klimatskih razmer, saj se v veliki meri odvija na prostem. Od vremenskih dejavnikov imajo največji vpliv temperature in padavine ter ekstremni vremenski dogodki, med katere prištevamo tudi kmetijsko sušo. Označuje se jo kot obdobje, ko imamo nezadostno količino vode v tleh, ki jo kmetijske rastline potrebujejo za normalen razvoj. Kmetijska suša je postala globalen problem, saj v svoji obsežnosti ovira prehransko varnost držav. Zajema vse države sveta in je občutno prisotna na 30 % kopenske površine, ekstremna suša pa na 3-5 % le te. Gre za obsežen pojav, ki najbolj ogroža države severovzhodne Afrike in jugozahodne Azije s Kitajsko. Tudi Slovenija ima kljub sorazmerno veliki povprečni letni količini padavin vse več let s sušami, povečuje se pogostost in intenziteta. Najbolj sušno ogrožena območja so vzhodni, južni in obalni predeli Slovenije. Pojav zajema 25 % celotne površine naše države. Scenariji napovedanih podnebnih sprememb kažejo, da se bodo težave zaradi suš v prihodnosti še stopnjevale zaradi napovedanih višjih temperature zraka (1 do 4 °C, odvisno od scenarija) in povečanega izhlapevanja (do 16 %). Padavin bo manj predvsem poleti in v času vegetacije rastlin. Suše bodo pogostejše in intenzivnejše in se bodo pojavljale na območjih, kjer jih do sedaj ni bilo. Glede na sedanje stanje in napovedane spremembe podnebja je prilagajanje kmetijstva na sušo nujen ukrep, potrebno bo spremljanje stanja in sprotno obveščanje o stanju sušnosti, načrtovanje namakalnih sistemov, prilagajanje agrotehničnih ukrepov, uvajanje novih, na sušne razmere odpornejših sort in spremembe kmetijske zakonodaje. Agriculture is a series of activities that are highly dependent on weather and climate conditions, as they take place mostly outdoors. Temperature and precipitation have the greatest impact on agriculture, as do extreme weather events, which include agricultural drought. It is described as a period when we have an insufficient amount of water in the soil that agricultural plants need for normal growth and development. Agricultural drought has become a global problem as it obstructs the food security of countries in its scale. It affects all the countries of the world, covering 30 % of the land area, while 3-5 % of it is affected by extreme drought. It is a large-scale phenomenon that threatens the countries of Northeast Africa and Southwest Asia including China. Despite the relatively high average annual rainfall, Slovenia also experiences periods of droughts, the frequency and intensity of which are increasing. The most drought-endangered areas are the eastern, southern and coastal parts of Slovenia. Drought is likely to occur on 25 % of all areas in our country. Scenarios of forecasted climate change indicate that drought problems will intensify in the future due to the predicted higher air temperatures (1 to 4 °C, depending on the scenario) and increased evaporation (up to 16 %). There will be less precipitation, especially in summer and during the vegetation period. Droughts will be more frequent and more intense and will occur in areas where they have not been recorded before. In view of the current situation and the predicted climate change, the adaptation of agriculture to drought is a necessary. It will be very important in the future to monitor and spread information on drought, plan more irrigation systems, include more various agro-technical measures, introduce new drought-resistant crops and change some agricultural legislation.

As the global temperature increases with changing climate, precipitation rates and patterns are affected through a wide range of physical mechanisms. The globally averaged intensity of extreme precipitation also changes more rapidly than the globally averaged precipitation rate. While some aspects of the regional variation in precipitation predicted by climate models appear robust, there is still a large degree of intermodel differences unaccounted for. Individual drivers of climate change initially alter the energy budget of the atmosphere, leading to distinct rapid adjustments involving changes in precipitation. Differences in how these rapid adjustment processes manifest themselves within models are likely to explain a large fraction of the present model spread and better quantifications are needed to improve precipitation predictions. Here, the authors introduce the Precipitation Driver and Response Model Intercomparison Project (PDRMIP), where a set of idealized experiments designed to understand the role of different climate forcing mechanisms were performed by a large set of climate models. PDRMIP focuses on understanding how precipitation changes relating to rapid adjustments and slower responses to climate forcings are represented across models. Initial results show that rapid adjustments account for large regional differences in hydrological sensitivity across multiple drivers. The PDRMIP results are expected to dramatically improve understanding of the causes of the present diversity in future climate projections.

article i nfo Aluminum nitride Thin film Atomic layer deposition Self-limiting growth Trimethylaluminum Wurtzite We report on the self-limiting growth and characterization of aluminum nitride (AlN) thin films. AlN films were deposited by plasma-enhanced atomic layer deposition on various substrates using trimethylaluminum (TMA) and ammonia (NH3). At 185 °C, deposition rate saturated for TMA and NH3 doses starting from 0.05 and 40 s, respectively. Saturative surface reactions between TMA and NH3 resulted in a constant growth rate of ~0.86 A/cycle from 100 to 200 °C. Within this temperature range, film thickness increased linearly with the number of deposition cycles. At higher temperatures (≥225 °C) deposition rate increased with tem- perature. Chemical composition and bonding states of the films deposited at 185 °C were investigated by X- ray photoelectron spectroscopy. High resolution Al 2p and N 1s spectra confirmed the presence of AlN with peaks located at 73.02 and 396.07 eV, respectively. Films deposited at 185 °C were polycrystalline with a hex- agonal wurtzite structure regardless of the substrate selection as determined by grazing incidence X-ray dif- fraction. High-resolution transmission electron microscopy images of the AlN thin films deposited on Si (100) and glass substrates revealed a microstructure consisting of nanometer sized crystallites. Films exhibited an optical band edge at ~5.8 eV and an optical transmittance of >95% in the visible region of the spectrum.

Due to improved kinetics and reduced CO poisoning effects, higher temperature alcohol fuel cells have been shown to have higher activity and increased performance output when compared to lower temperature alcohol fuel cells. In this work, the Direct Alcohol Phosphoric Acid Fuel Cell (DAPAFC) with methanol and ethanol as reactant fuels, and Pt and PtRu as catalysts is studied. The electrolyteseparator consists of Phosphoric Acid in a Silicon Carbide (SiC) matrix and replaces conventional polymer electrolyte or PBI membranes. Comprehensive studies are conducted to demonstrate the performance effects of the Gas Diffusion Layer (GDL), Micro-porous Layer (MPL) and such parameters as the stream pressures, higher temperature operation (120-180°C), and the thickness of the SiC separator, etc. Results show that at the same operating conditions, the cell performance is comparable to that of a vapour fed Nafion membrane based fuel cell. Structure improvement of the Phosphoric Acid Electrode Assembly (PAEA) and reactant vapor composition can significantly improve durability. This type of fuel cell demonstrates performance improvement and stability in a higher temperature range than is possible with the conventional PEMFC. © 2012 The Electrochemical Society.

The primary objective of this work is to characterize and compare the dynamic mechanical behavior of asphalt concrete mixes with styrene butadiene styrene (SBS) polymer and crumb rubber modified asphalt binders with the behavior of mixes with unmodified viscosity grade asphalt binders. Asphalt binders are characterized for their physical and rheological properties. Simple performance tests like dynamic modulus, dynamic and static creep tests are carried out at varying temperatures and time. Dynamic modulus master curves constructed using numerical optimization technique is used to explain the time and temperature dependency of modified and unmodified asphalt binder mixes. Creep parameters estimated through regression analysis explained the permanent deformation characteristics of asphalt concrete mixes. From the dynamic mechanical characterization studies, it is found that asphalt concrete mixes with SBS polymer modified asphalt binder showed significantly higher values of dynamic modulus and reduced rate of deformation at higher temperatures when compared to asphalt concrete mixes with crumb rubber and unmodified asphalt binders. From the concept of energy dissipation, it is found that SBS polymer modification substantially reduces the energy loss at higher temperatures. Multi-factorial analysis of variance carried out using generalized liner model showed that temperature, frequency and asphalt binder type significant influences the mechanical response of asphalt concrete mixes. The mechanical response of SBS polymer modified asphalt binders are significantly correlated with the rutting resistance of asphalt concrete mixes. � 2011 Elsevier B.V.

Experiments were conducted for microwave heating and melting of lead, tin, aluminium and copper with the aid of susceptors and the detailed results were presented for various microwave power levels and sample loading. Aluminium and copper samples were heated in presence of inert gas to minimize oxidation. Compared to conventional melting, microwave melting was twice as fast and more energy efficient. Lumped parameter model of the heating process showed that the conversion of microwave to thermal energy was enhanced at higher temperatures, justifying this a favourable process for metal melting applications. � 2010 Elsevier B.V. All rights reserved.

This work presents the ionic transport properties in some nanocrystalline double doped cerias, i.e., Ce0.8Gd0.1Pr 0.1O2-? and Ce0.8Gd0.15Pr 0.05O2-? with various average grain sizes, in the intermediate temperature region. The correlations between electrical and dielectric properties of these materials have been established and variation of conductivity with respect to temperature has been thoroughly discussed. All the materials are found to be ionic in nature and show high value of ionic conductivity at intermediate temperatures. The nanocrystalline Ce 0.8Gd0.1Pr0.1O2-? material (irrespective of grain size), shows lowest association energy, i.e., 0.03 eV, which is close to the theoretically predicted lowest value (0.02 eV) in double doped ceria. A repulsive force is expected between the free oxygen vacancies at the grain boundary regions at higher temperatures, which restricts the rise in grain boundary conductivity and results in decrease in total conductivity. � 2010 Elsevier Ltd. All rights reserved.

In the present study, influence of microstructure on high temperature dry sliding wear behavior of nickel base hardfaced coating is discussed in detail. Using plasma transferred arc (PTA) welding process, coating of nearly 4 to 5. mm thickness was deposited on 316 L (N) stainless steel substrate without any defects. The as-deposited coating contains large quantity of precipitates (range from 100nm to 20?m in size) in the ?-nickel matrix which increased the hardness significantly. Sliding wear tests were carried out on the coating for different sliding distances at room temperature (RT) and also higher temperature (573. K, and 823. K). Results showed that the wear resistance of coating improved significantly with increase in test temperature, and the high wear resistance was observed at 823. K. The coating exhibited different operating wear mechanisms depending on sliding distances and also test temperature. The wear mechanisms were identified based on friction and wear values along with worn surface analysis. The operating wear mechanisms at 823. K are adhesion at shorter sliding distance and tribo-oxidation at longer sliding distance. � 2010 Elsevier B.V.

We report transient spectral hole-burning studies of the R-2(+/- 1/2) line in 130, 20 ppm and 0.6 ppm ruby between 2.4 and 70 K. The homogeneous line width Gamma(h) is found to be 142 +/- 6 MHz at 2.4 K for both 20 and 130 ppm crystals; this value is in agreement with the T-1 value of 1.1 ns (Gamma(h) = 1/2 pi T-1 = 140 MHz) for the 2 (A) over bar state obtained by Rives and Meltzer who used pulsed, non-selective laser excitation. The line width is dominated by a direct one-phonon relaxation process 2 (A) over bar -> (E) over bar up to 50 K whereas at higher temperatures two-phonon Raman scattering becomes dominant. Cross-relaxation and spin-lattice relaxation times significantly affect pseudo-CW experiments. Refereed/Peer-reviewed

A novel approach to the oxidation mechanism of near-stoichiometric TiC is presented. It is confirmed by consideration of solid-state chemical kinetics model and electron microscopy observations in parallel. At low oxygen pressures and moderate temperatures the initial step of the process is connected with the dissolution of oxygen and subsequent decomposition of oxygen-oversaturated oxycarbide, which ultimately results in the nucleation of oxide phase, in particular anatase, belike stabilised by residual carbon. An anatase-rutile transformation is concurrent with deeper carbon burn-off in the oxide scale, which sinters at higher temperatures. This mechanism shifts the process to a gas diffusion regime, governed by the scale permeability, but determined by solid-state diffusion that is reflected in the kinetics, as further temperature increase is accompanied by a decrease of the oxidation rate, so in general the process is characterised by the negative value of apparent activation energy. © 2008 Elsevier B.V. All rights reserved.

A study on grinding with resin bonded and plated diamond abrasive wheels have been carried out to evaluate the significance of bond on wheel performance. The performance indicators namely grinding force, acoustic emission signals emanating from the workpiece and temperature were monitored. Surface finish of the machined surface was measured using a perthometer. The electroplated wheel experiences higher order grinding force components compared to resin bonded wheel, since resin bonded diamond wheel presents sharper/keen edged abrasives, unlike the presence of smeared abrasive in case of plated wheel. The acoustic emission (AE) power spectra for the electroplated wheel shows dominant low frequency peaks of relatively higher order compared to resin bonded wheel. This can be attributed to sliding dominated grinding associated with higher order grinding force components. The electroplated wheel experiences higher temperature with low depth of grinding, while a visible reduction in temperature can be seen with higher depth of grinding. Resin bonded wheel gave better surface finish compared to the electroplated wheel. As a whole, resin bonded wheel performed better than electroplated wheel. � 2008 Elsevier Ltd. All rights reserved.

Au and Au-Pt alloy nanoparticles are prepared and patterned at room temperature within the PMMA polymer matrix by the action of 254 nm UV light or X-rays. The polymer matrix enables us to entangle the kinetics of the photochemical reduction from the nucleation and growth processes, when monitored by UV-vis spectroscopy. Accordingly, increase of the temperature to 50 degrees C of the reaction medium increases the nucleation and growth rates of the nanoparticle formation by more than one order of magnitude, due to enhanced diffusion and nucleation at the higher temperature, but has no effect on the photochemical reduction process. Presence of Pt ions also increases the same rate, but by a factor two only. Similar photochemical reduction and particle growth take also place within the PMMA matrix, when these metal ions are subjected to prolonged exposure to X-rays, as evidenced by XPS analysis. Both angle-resolved and charge-contrast measurements using XPS reveal that the resultant Au and Pt species are in close proximity to each other, indicating the Au-Pt alloy formation to be the most likely case. (C) 2008 Elsevier Ltd. All rights reserved.

International audience; Asphaltenes are the polar macromolecules with complex structures in oils, usually existing as aggregates. Inside the macromolecular structures of asphaltenes, some other fractions can be adsorbed/occluded, and the occluded compounds contain some important geochemical information. However, the adsorption/occlusion phenomena of asphaltenes need verification. Thus, this work was aimed to experimentally study the adsorption/occlusion processes inside the asphaltenes, using the deuterated paraffin n-C 20D 42 as the target compound under the conditions of high temperature/high pressure, with some chloride salts as additives to probe the mechanism of the adsorption/occlusion inside asphaltenes. The results show that the adsorption/occlusion phenomena take place inside asphaltenes during their thermal evolution. Occlusion inside asphaltenes could occur via two paths, namely, the physical process maybe through the polar interactions among the molecules and the chemical process through condensation or polymerization of the molecules, and then some substantial microporous units could develop to adsorb/occlude other fractions. The temperature and the additives have influences on the occlusion taking place inside asphaltenes. Higher temperatures promoted the pyrolysis of asphaltenes, and the additives play an important role in the properties of adsorption/occlusion inside asphaltenes.

A redshift of the peak emission wavelength was observed in the blue light emitting diodes of InGaN/GaN grown with a higher temperature interlayer that was sandwiched between the low-temperature buffer layer and high-temperature unintentionally doped GaN layer. The effect of interlayer growth temperature on the emission wavelength was probed and studied by optical, structural, and electrical properties. Numerical studies on the effect of indium composition and quantum confinement Stark effect were also carried out to verify the experimental data. The results suggest that the redshift of the peak emission wavelength is originated from the enhanced indium incorporation, which results from the reduced strain during the growth of quantum wells. © 2012 American Institute of Physics.

The occurrence, distribution, and temperature dependence in the marine atmosphere of several alternative brominated flame retardants (BFRs), Dechlorane Plus (DP) and polybrominated diphenyl ethers (PBDEs) were investigated during a sampling cruise from the East Indian Archipelago toward the Indian Ocean and further to the Southern Ocean. Elevated concentrations were observed over the East Indian Archipelago, especially of the non-PBDE BFR hexabromobenzene (HBB) with concentrations up to 26 pg m-3 which were found to be related to continental air masses from the East Indian Archipelago. Other alternative BFRs- pentabromotoulene (PBT), pentabromobenzene (PBBz), and 2,3-dibromopropyl-2,4,6-tribromophenyl ether (DPTE)-were elevated, too, with concentrations up to 2.8, 4.3, and 2.3 pg m-3, respectively. DP was detected from 0.26 to 11 pg m-3 and bis-(2-ethylhexyl)- tetrabromophthalate (TBPH) ranged from not detected (nd) to 2.8 pg m -3, respectively. PBDEs ranged from nd to 6.6 pg m-3 (∑10PBDEs) with the highest individual concentrations for BDE-209. The approach of Clausius-Clapeyron (CC) plots indicates that HBB is dominated by long-range atmospheric transport at lower temperatures over the Indian and Southern Ocean, while volatilization processes and additional atmospheric emissions dominate at higher temperatures. In contrast, BDE-28 and -47 are dominated by long-range transport without fresh emissions over the entire cruise transect and temperature range, indicating limited fresh emissions of the meanwhile classic PBDEs.

This paper presents the results of investigations on the rheological properties of modified asphalt binders and their influence on the performance of asphalt mixes. Asphalt mixes with modified binders such as styrene butadiene styrene polymer, crumb rubber, natural rubber, and waste plastics were evaluated for their rheological properties and compared to the properties of asphalt mixes with unmodified VG30 (viscosity grade) asphalt binder. The dynamic modulus values and rutting characteristics of the asphalt mixes were studied with due consideration to different levels of aging and temperature variations. Studies on the rheological properties showed that the energy dissipated by unmodified asphalt (VG30) binder is higher than that of modified asphalt binders. Long-term aged natural rubber and waste plastic modified asphalt binders showed significant increase in the properties compared to unmodified asphalt binder (VG30). Reduced temperature susceptibility of polymer modified asphalt binder showed that only polymer modification can enhance both high temperature rutting resistance and low temperature thermal cracking resistance of asphalt mixes. The transient nature of polymer modified asphalt mix from viscoelastic solid-like to viscoelastic fluid-like condition is significantly shifted to higher temperature compared to that of the mix with unmodified asphalt binder. Aging and rutting indices showed that rubber modified asphalt mixes are highly susceptible to aging. Statistical analysis of test results showed that the process of modification of asphalt binder, aging, and temperature during the test influence the rheological and rutting characteristics of asphalt mixes significantly. Correlation between the asphalt binder properties and its influence on the rutting resistance are found to be statistically significant. The analysis using least significant difference showed that polymer modified asphalt binder significantly improves the aging and rutting resistance of asphalt mixes compared to unmodified asphalt binder. Copyright � 2012 by ASTM International.

ZnO nanowires (NWs) with diameters of 50 to 250 nm and lengths of several micrometres have been grown by reactive vapour transport via the reaction of Zn with oxygen on 1 nm Au/Si(001) at 550°C under an inert flow of Ar. These exhibited clear peaks in the X-ray diffraction corresponding to the hexagonal wurtzite crystal structure of ZnO and a photoluminescence spectrum with a peak at 3.3 eV corresponding to band edge emission close to 3.2 eV determined from the abrupt onset in the absorption-transmission through ZnO NWs grown on 0.5 nm Au/quartz. We find that the post growth nitridation of ZnO NWs under a steady flow of NH 3 at temperatures ≤600°C promotes the formation of a ZnO/Zn 3N 2 core-shell structure as suggested by the suppression of the peaks related to ZnO and the emergence of new ones corresponding to the cubic crystal structure of Zn 3N 2 while maintaining their integrity. Higher temperatures lead to the complete elimination of the ZnO NWs. We discuss the effect of nitridation time, flow of NH 3, ramp rate and hydrogen on the conversion and propose a mechanism for the nitridation. © 2012 Zervos et al. 7 1 8 Cited By :1

The structure, dielectric and magnetic properties of complex Sr2FeTiO6 double perovskite have been investigated. Reitveld analysis of X-ray powder diffraction pattern reveals that the material is stabilized in a cubic perovskite phase with Pm (3) over barm space group without the B-site cations ordering. The temperature evolution of crystal structural studies indicates the absence of structural changes with temperature. The scanning electron micrograph exhibits heterogeneous grain distribution with average grain size of 1-7.5 mu m. The bond valence sum calculations and diffusion-assisted small-polaron hopping conduction mechanism confirm the mixed valence state of Fe/Ti ions. Dielectric spectra show a broad dielectric anomaly coupled with a shift in dielectric maxima towards higher temperature with frequency, exhibiting a typical relaxor ferroelectric behavior. The relaxor behavior has been quantitatively characterized based on the phenomenological parameters (T-m, T-B, gamma, Delta T-relax). The agreement of dielectric relaxation with non-linear Vogel Fulcher relation indicates that the system is indeed a relaxor exhibiting glassy characteristics. The transport studies show a semiconductor like behavior and a negligible magnetoresistance. Furthermore, the magnetic characterisation exhibits a non-metallic spin-glass-like state below 16 K, driven by competing interactions between the antiferromagnetic and the ferromagnetic states. (C) 2012 Elsevier B. V. All rights reserved.

cited By 3; International audience; Thermal stability of (Ce0.72Cu0.28)90-xAl10Fex (x= 0, 5 or 10) bulk metallic glasses (BMGs) was analyzed by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Temperatures corresponding to glass transition (Tg), onset of crystallization (Tx) and crystallization peak (Tp) shift to higher temperature by increasing the Fe content. Kissinger model allows calculating the effective activation energy Ea of the crystallization process. For the first crystalline peak, energies are 1.47 eV, 1.50 eV and 1.58 eV for x = 0, 5 and 10, respectively, implying that effective activation energy Eaof the crystallization process increases by increasing the Fe content. In the iron-free alloy, a second crystalline peak is observed, with activation energy of 2.3 eV. Influence of microstructure modifications on elastic and viscoelastic properties was investigated by dynamic mechanical analysis (DMA). © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

We report on optically pumped lasing at 500 nm on InGaN laser structures grown by plasma assisted molecular beam epitaxy. The InGaN laser structures were grown under group III-rich conditions on bulk (0001) GaN substrates. The influence of the nitrogen flux and growth temperature on the indium content of InGaN layers was studied. We demonstrate that at elevated growth temperatures, where appreciable dissociation rate for In-N bonds is observed, the indium content of InGaN layers increases with increasing nitrogen flux. We show that growth of InGaN at higher temperatures improves optical quality of InGaN quantum wells, which is crucial for green emitters. The influence of piezoelectric fields on the lasing wavelength is also discussed. In particular, the controversial issue of partial versus complete screening of built-in electric field at lasing conditions is examined, supporting the former case. © 2011 American Institute of Physics.

A set of knitted poly(lactic acid) (PLA) fabrics was ozonated at room temperature for periods ranging from one to 60 minutes in order to identify any accompanying effects on physical properties (specifically whiteness, water-absorbency, flexural rigidity and burst strength), fiber surface integrity or internal microstructure. A significant (ca. 6% after 10 minutes of treatment) initial increase in whiteness was observed, with longer treatment times producing little further change. The fabric’s absorbency and flexibility both increased, the time of wetting having fallen by ca. 20% and the flexural rigidity by ca. 16%, respectively, after 10 minutes of treatment. Fabric strength remained virtually unaffected for short times (up to 10 minutes) of ozonation, although longer treatments caused a measurable drop (ca. 10% after 60 minutes). SEM imaging showed virtually no evidence for surface damage, even after 60 minutes of treatment, whereas peroxide treatment caused massive pitting of the fiber surface. Raman spectroscopy of the ozonated PLA fabrics indicated that the treatment had not affected the internal microstructure of the fibers. Our conclusion is that brief (no more than 10 minutes) room-temperature ozonation is potentially an effective, safe and low-energy alternative to conventional higher temperature peroxide treatment. © 2011, SAGE Publications. All rights reserved.

In the present work, we report the temperature dependent carrier transport properties of InxGa1-xN thin films in the entire composition range grown by modified activated reactive evaporation. The carrier transport in these degenerate semiconductors is controlled by impurity band conduction. A transition from metallic to semiconducting type resistivity was observed for indium rich films. The semiconducting behavior originates from electron-electron interaction and weak localization, whereas higher temperature scattering contributes to the metallic type resistivity. A transition of resistivity behavior from the quantum phenomena to the classical Arrhenius approach was observed for x 0.12 film. � 2011 American Institute of Physics.

BaO x(0.5 MLE-10 MLE)/Pt(111) (MLE: monolayer equivalent) surfaces were synthesized as model NO x storage reduction (NSR) catalysts. Chemical structure, surface morphology, and the nature of the adsorbed species on BaO x/Pt(111) surfaces were studied via X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption (TPD), and low-energy electron diffraction (LEED). For θ BaOx < 1 MLE, (2 × 2) or (1 × 2) ordered overlayer structures were observed on Pt(111), whereas BaO(110) surface termination was detected for θ BaOx = 1.5 MLE. Thicker films (θ BaOx ≥ 2.5 MLE) were found to be amorphous. Extensive NO 2 adsorption on BaO x(10 MLE)/Pt(111) yields predominantly nitrate species that decompose at higher temperatures through the formation of nitrites. Nitrate decomposition occurs on BaO x(10 MLE)/Pt(111) in two successive steps: (1) NO(g) evolution and BaO 2 formation at 650 K and (2) NO(g) + O 2(g) evolution at 700 K. O 2(g) treatment of the BaO x(10 MLE)/Pt(111) surface at 873 K facilitates the BaO 2 formation and results in the agglomeration of BaO x domains leading to the generation of exposed Pt(111) surface sites. BaO 2 formed on BaO x(10 MLE)/Pt(111) is stable even after annealing at 1073 K, whereas on thinner films (θ BaOx = 2.5 MLE), BaO 2 partially decomposes into BaO, indicating that small BaO 2 clusters in close proximity of the exposed Pt(111) sites are prone to decomposition. Nitrate decomposition temperature decreases monotonically from 550 to 375 K with decreasing BaO x coverage within θ BaOx = 0.5 to 1.0 MLE. Nitrate decomposition occurs at a rather constant temperature range of 650-700 K for thicker BaO x overlayers (2.5 MLE < θ BaOx < 10 MLE). These two distinctly characteristic BaO x-coverage-dependent nitrate decomposition regimes are in very good agreement with the observation of the so-called "surface" and "bulk" barium nitrates previously reported for realistic NSR catalysts, clearly demonstrating the strong dependence of the nitrate thermal stability on the NO x storage domain size. © 2011 American Chemical Society.

After disposal in nuclear waste repositories the chemical and migration behavior of actinides depends on many factors. It is estimated that maximum temperatures in the near field of a repository could reach 300°C in dependence on the waste forms [1] and the host rock [2]. Thus, for the long-term safety assessment, knowledge of the interaction of actinides such as uranium with inorganic and organic ligands at elevated temperatures is required. The amount of organic matter in a repository can be separated in humic substances and in low molecular weight organic substances. A not negligible component of low molecular weight organic substances is the group of carboxylic acid. For example, citric acid is used in nuclear reprocessing [3] and acetic, lactic and formic acid were identified in rock extracts and pore water of Opalinus Clay [4]. Reliable experimental data on the complexation of U(VI) in solution at elevated temperatures are still needed. Therefore, we studied the U(VI) complexation by lactic acid (pH 3) and citric acid (pH 0-10) in the temperature range from 7 to 65°C. Species distribution and complex formation constants were determined by means of UV-Vis and time-resolved laser-induced fluorescence spectroscopy. In the U(VI) lactate system, we identified the formation of 1:1- and 1:2-complexes. In the presence of citrate, we could characterize five U(VI) complexes in dependence on pH value. The complex formation between U(VI) and these both ligands was found to be endothermic and entropy-driven. The complex stability constants of the U(VI) complexes increase with increasing temperature. This could lead to an increased mobility of U(VI) at higher temperatures.

A new TiAl-4Nb-3Mn beta gamma alloy was synthesised by a powder metallurgy process. HIPed and vacuum heat treated specimens were isothermally oxidised at 800 and 900°C in air up to 500 h. The TiAl-4Nb-3Mn alloys oxidised parabolically up to 500 h at both 800 and 900°C. The oxides consisted of outer TiO2 layer, intermediate Al2O3 layer and inner TiO2 rich mixed layer and the oxidation mechanisms of the alloy were identical at both temperatures. During oxidation, the degradation of a2 lamellae in the vicinity of the interface forms a diffusion zone (lamellar depleted zone) leading to the formation of Nb and Mn rich white layers just below the interface by outward diffusion of Nb and Mn which are released from breakdown of α2 lamellae. As exposure time increases, Nb begins to diffuse earlier than Mn and diffuses more actively at higher temperature. The activation energy for oxidation of TiAl-4Nb-3Mn alloy was lower than that of Ti-48Al alloy and was higher than those of Ti-48Al-2Nb-2Cr and Ti-48Al-2Nb-2Cr-W alloys. © 2011 Canadian Institute of Mining, Metallurgy and Petroleum.

A new superalloy, ATI 718Plus alloy (718Plus), has been developed to have a 55°C higher temperature capability over the traditionally used alloy 718, while maintaining favourable processing characteristics and intrinsic raw material costs. The fatigue and dwell fatigue behaviour of four microstructural variations of 718Plus are evaluated and compared with Waspaloy: standard heat treated condition (HT1), standard heat treated condition with thermal exposure at 732°C (1350°F) for 1000 h (HT2), fine grain condition with a modified d phase (HT3) and fine grain overaged through modified heat treatment (HT4). Fatigue crack growth rate tests were performed at 649°C (1200°F) and 704°C (1300°F) under constant amplitude loading at 10 Hz or with a 100 s tension dwell. The results show that the steady state fatigue crack growth rates of each microstructural variation and both alloys are identical, with all of the 718Plus variations showing a clear advantage over Waspaloy in the fatigue crack threshold regime. The 718Plus variants HT1 and HT3 exhibited the highest fatigue crack growth threshold, followed closely by HT4 and finally HT2. At 649°C (1200°F), the 718Plus alloys had average threshold values ranging from 8·8 to 10·4 MPa m1/2 whereas the Waspaloy material was 6·1-7·5 MPa m1/2. At 704°C (1300°F), the advantage increased with the 718Plus alloys having average threshold values ranging from 10·1 to 11·6 MPa m1/2 compared with Waspaloy, which exhibited average threshold values of 6·6-7·7 MPa m1/2. Dwell fatigue results show that Waspaloy has better resistance to crack propagation under dwell conditions; however, optimisation of the precipitate phase (HT2) shows vast improvement in the dwell fatigue resistance of 718Plus. © 2011 Canadian Institute of Mining, Metallurgy and Petroleum.

Because of the renewable nature, emission advantage, and easy adaptation, vegetable-oil-based fuels are emerging as the most promising alternatives to fossil diesel for use in compression-ignition engines. In this study, a unified approach is proposed for predicting the densities of straight and processed vegetable oils from their fatty acid composition, obviating the need of measured values particularly for use in process modeling studies. The proposed methodology has been validated using the measured densities of 11 different vegetable oils and 13 different processed vegetable oils. The predictions are found to be in good agreement (?1% error) even at higher temperatures up to 90 �C. � 2010 American Chemical Society.

Electrical and dielectric properties, and their correlations were discussed in the nanostructured Ce0.8 Dy0.2 O2-? materials with average grain sizes of 15, 35, and 58 nm using the dielectric functions such as dielectric permittivity (??), loss tangent (tan ?), and electric modulus (M?). The ionic transport mechanism varies with the grain size of the materials such that the material with an average grain size of 35 nm exhibited a higher value of ionic conductivity above 440�C (with ?=8.96� 10-4 S cm-1 at 550�C), whereas the material with an average grain size of 15 nm shows higher value conductivity at lower temperatures. The oxygen vacancy in the material decreases with the decrease in grain size. The migration energy of oxygen ions also decreases with the decrease in grain size of the nanostructured Ce0.8 Dy 0.2 O2-? material. The material with an average grain size of 35 nm shows a very low value association energy (i.e., 0.05 eV) compared to the others. At temperatures below 420�C, the local motion of oxygen vacancies around Dy+3 controls the conductivity of all the materials, and at higher temperatures, the conductivity in the materials with a larger grain size is mainly due to the long-range motion of vacancies. � 2010 The Electrochemical Society.

Wear behaviours of aluminum silicon alloy and AlSi/graphite composite were investigated at ambient and elevated temperatures. The trend showed a decrease in wear rate with increase in temperature. The reduction in wear rate was mainly attributed to the formation of glazing layer and oxide layer at higher temperature. This was invariably observed in alloy and composites. In addition, the presence of graphite in composite offered better wear resistance for all temperatures under consideration. The wear due to oxidation was predominant during high temperature sliding. � 2010 Elsevier Ltd.

Magnetization measurements on a single crystal of the high-Tc cuprate HgBa2CuO4 (Hg-1201) are performed for the two field orientations B||c and B||(a, b). Besides zero-field-cooling (zfc) - field-cooling (fc) and magnetization studies, the flux creep relaxation is determined. The zfc curves exhibit pronounced step-like anomalies in the mixed state above the lower critical field Bc1. They are interpreted as those points in the phase diagram where the penetrating flux fronts meet at the center of the sample. In order to obtain more information about the flux pinning mechanism flux creep relaxation experiments are performed at different temperatures in magnetic fields of 0.15 and 2 T. The resulting supercurrent dependence on the mean activation energy is analysed according to the collective pinning theory which predicts U ((j/jc)-μ -1). The μ- values for B||c are 0.5 at higher temperatures and 2 at 5 K, and they vary between 1.1 and 1.5 for B||(a, b). The observed behaviour is quite different from that found for powder samples

Electrospinning of nanofibers with cyclodextrin inclusion complexes (CD-ICs) is particularly attractive since distinct properties can be obtained by combining the nanofibers with specific functions of the CD-ICs. Here we report on the electrospinning of poly(methyl methacrylate) (PMMA) nanofibers containing cyclodextrin-menthol inclusion complexes (CD-menthol-ICs). These CD-menthol-IC functionalized nanofibers were developed with the purpose of producing functional nanofibers that contain fragrances/flavors with high temperature stability, and menthol was used as a model fragrance/flavor material. The PMMA nanofibers were electrospun with CD-menthol-ICs using three type of CD: alpha-CD, beta-CD, and gamma-CD. Direct pyrolysis mass spectrometry (DP-MS) studies showed that the thermal evaporation of menthol occurred over a very high and a broad temperature range (100-355 degrees C) for PMMA/CDmenthol-IC nanowebs, demonstrating the complexation of menthol with the CD cavity and its high temperature stability. Furthermore, as the size of CD cavity increased in the order alpha-CDbeta-CDgamma-CD, the thermal evolution of menthol shifted to higher temperatures, suggesting that the strength of interaction between menthol and the CD cavity is in the order gamma-CDbeta-CDalpha-CD.

Miniaturization of biosensors is envisaged by the development of biochips consisting of parallel microarray patterns of binding sites on rigid substrates, such as glass or silicon. Thin plastic substrates are promising flexible alternatives because of the possibility for large-area roll-to-roll manufacturing of disposable chips at lower costs. Mature optical lithography technology faces many challenges when used to pattern flexible foils as a result of the substrate instabilities, especially at higher temperatures. In this work, flexible biochips with gold electrode patterns were fabricated on thin polyethylene naphthalate (PEN) foils using photolithography. The gold electrode structures of the chips were manufactured by direct metal patterning and by lift-off processing. Both methodologies resulted in well-defined electrode patterns as concluded from optical microscopy and scanning electron microscopy (SEM) characterization and resistance measurements. The biochips were successfully employed for the electrical and optical detection of DNA molecules. The DNA detection was based on the immobilization of capture DNA between electrode gaps, hybridization with biotin-labeled target DNA, and enzymatic silver enhancement. © 2009 American Chemical Society.

Miniaturization of biosensors is envisaged by the development of biochips consisting of parallel microarray patterns of binding sites on rigid substrates, such as glass or silicon. Thin plastic substrates are promising flexible alternatives because of the possibility for large-area roll-to-roll manufacturing of disposable chips at lower costs. Mature optical lithography technology faces many challenges when used to pattern flexible foils as a result of the substrate instabilities, especially at higher temperatures. In this work, flexible biochips with gold electrode patterns were fabricated on thin polyethylene naphthalate (PEN) foils using photolithography. The gold electrode structures of the chips were manufactured by direct metal patterning and by lift-off processing. Both methodologies resulted in well-defined electrode patterns as concluded from optical microscopy and scanning electron microscopy (SEM) characterization and resistance measurements. The biochips were successfully employed for the electrical and optical detection of DNA molecules. The DNA detection was based on the immobilization of capture DNA between electrode gaps, hybridization with biotin-labeled target DNA, and enzymatic silver enhancement. © 2009 American Chemical Society.

Mesoporous Al-Ti mixed oxides have been prepared by employing pyrrole-based nitrogen-doped mesoporous carbon templates with p6mm and Im3m symmetries. These oxides were obtained using isopropanol solutions of aluminum and titanium isopropoxides, Al(PriO)3 and Ti(PriO) 4, respectively, by a combined nanocasting and sol - gel synthesis, involving hydrolysis of the aforementioned precursors in the pores of the carbon templates, followed by controlled thermal treatment of the resulting composites in nitrogen and oxidative removal of the templates in flowing air at 700 °C. The resulting mixed oxides and corresponding oxide-carbon nanocomposites were characterized by thermogravimetry, CHNS elemental analysis, nitrogen adsorption at -196 °C, small and wide angle X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy (HR TEM), energy-dispersive X-ray spectrometry (EDX), and elemental mapping. Nitrogen adsorption revealed that the ordered mesopores of the carbon templates were almost completely filled in a single nanocasting step, and the oxide inverse replicas possessed a specific surface area of about 200 m2/g, large pore volume, and uniform mesopores. The corresponding pore size distributions are narrow and centered at ∼7 nm; the latter value showed a tendency to increase with increasing temperature of the thermal treatment preceding the oxidative removal of the carbon template. In addition, HR TEM analysis confirmed ordered porosity of some oxide samples. The mixed oxide samples were found to be amorphous, if the temperatures of the thermal treatments in nitrogen and air did not exceed 700 °C. At higher temperatures, crystalline phases were gradually formed. The wide angle XRD analysis of the mixed oxides treated at 1000 °C revealed the presence of R-Al2O3 and rutile TiO2 phases. For some nanocomposites, the Magnéli phase Ti6O11 was also detected. Because the carbon templates used possessed iron phases due to employing iron chloride to catalyze polymerization of pyrrole during carbon synthesis, this residual iron was oxidized during carbon removal and transferred to the resulting oxide replicas. Elemental mapping and EDX analysis revealed a homogeneous distribution of Al, Ti, and Fe for all amorphous samples of mixed oxides with the Al/Ti atomic ratios close to those used in the synthesis. Refereed/Peer-reviewed

A stochastic cellular automata simulator capable of spatiotemporal modeling of the crystallization and amorphization behavior of phase-change materials during the complex annealing cycles used in optical and electrical memory applications is presented. This is based on consideration of bulk and surface energies to generate rates of growth and decay of crystallites built up from "monomers" that may themselves be quite complex molecules. The approach uses a stochastic Gillespie-type time-stepping algorithm to deal with events that may occur on a very wide range of time scales. The simulations are performed at molecular length scale and using an approximation of local free energy changes that depend only on immediate neighbors. The approach is potentially capable of spanning the length scales between ab initio atomistic modeling methods, such as density functional theory, and bulk-scale methods, such the Johnshon-Mehl-Avrami-Kolmogorov formalism. As an example the model is used to predict the crystallization behavior in the chalcogenide Ge2 Sb2 Te5 alloy commonly used in phase-change memory devices. The simulations include annealing cycles with nontrivial spatial and temporal variations in temperature, with good agreement to experimental incubation times at low temperatures while modeling nontrivial crystal size distributions and melting dynamics at higher temperatures. � 2008 American Institute of Physics.

The catalytically important Mn/CeO2 - TiO2 (MCT) solid solutions were synthesized by solution combustion technique using glycine, urea, or PEG as fuel. These samples along with those prepared by coprecipitation and wet impregnation methods were characterized for its structural, textural and redox properties using various physical and spectroscopic techniques, viz., powder X-ray diffraction, high-resolution transmission electron microscopy, temperature-programmed reduction, diffuse reflectance UV - visible, electron paramagnetic resonance, and X-ray photoelectron spectroscopy. The samples prepared by the solution combustion method showed high thermal stability, even at temperatures of 1323 K, whereas the samples synthesized by conventional routes lost its structural integrity at higher temperatures due to fast sintering. The combustion and coprecipitation methods stabilize Mn species both in +2 and +3 oxidation states, while in the MCT sample prepared by wet impregnation, Mn ions are present in +3 state exclusively. The latter possesses highly reversible redox properties, whereas the samples prepared by combustion and coprecipitation techniques show quasireversible redox behavior. On comparing the physicochemical properties of MCT solid solutions with that of Mn/CeO2, we elucidate that Ti incorporation into the ceria matrix alters the redox properties of both cerium and manganese ions. Though the nature of the fuel did not have significant effect on the oxidation states of Mn species stabilized in the solid solutions, the relative concentration of Mn2+ and Mn3+ ions and their existence in the bulk or on the surface of the material did vary with the nature of the fuel used in the combustion process. These variations could be attributed to the intrinsic properties of combustion process, viz., the adiabatic/real flame temperature and mode of combustion and its duration. Employing PEG as fuel in the combustion process, one can obtain thermally stable nanocrystalline MCT samples with high phase purity. � 2008 American Chemical Society.