bluuebunny/crossref_metadata_2025_split huggingface dataset:
Physicochemical properties and creep strength of a single crystal of nickel-base superalloy containing rhenium and ruthenium
Authors: Petrushin Nikolay V. , Svetlov Igor L. , Samoylov Andrey I. , Morozova Galina I. 
Published: May 2010

Abstract
The influence of alloying elements, including rhenium and ruthenium, on the physicochemical and structural parameters of single crystal nickel-base superalloys has been analyzed. The results were used in computer designing of a single crystal nickel-base superalloy containing rhenium and ruthenium. The optimized alloy composition, providing the best physicochemical properties and longest creep lifetime, contains 6 wt.% rhenium and 4 wt.% ruthenium. <001> single crystals of the designed superalloy were directionally solidified and investigated in as-cast, heat treated and creep deformed conditions. The investigations included: characterization of the superalloy microstructure, dendritic segregation of alloying elements, their partition between the γ- and γ′-phases etc. Creep rupture tests were performed in the temperature interval of 900 – 1 100 °C and included tests longer 1 000 h.
Influence of heat treatment and microstructure on the tensile pseudoelastic response of an Ni-rich NiTi shape memory alloy
Authors: Bujoreanu Leandru-Gheorghe , Young Marcus L. , Gollerthan Susanne , Somsen Christoph , Eggeler Gunther 
Published: May 2010

Abstract
The influence of microstructure on the stress–strain behavior of an Ni-rich NiTi shape memory alloy is examined. Specimens cut from a large-diameter bar of Ni50.7Ti49.3 shape memory alloy were analyzed in two states: (i) annealed and (ii) annealed and aged. The annealed state shows a fully austenitic structure with no precipitates and no distortions caused by residual stresses. The annealed and aged state has coherent Ni4Ti3 particles precipitated in the proximity of the austenite grain boundaries. The size of the precipitates increases moving away from the grain boundaries toward the grain interiors. The evolution of the two states in the stress–strain–temperature space has been analyzed using tensile specimens with special geometry. Due to the complex effects of the coherent precipitates, the specimens in the aged state exhibited lower stress plateaus in the tensile loading–unloading curves, which enabled the occurrence of transformation pseudoelasticity from room temperature to 333 K.
Microstructural stability of an Ni–Mo based Hastelloy after 10 MeV electron irradiation at high temperature
Authors: Wanderka Nelia , Isheim Dieter , Bakai Alexander , Abromeit Christian , Seidman David N. 
Published: May 2010

Abstract
The microstructural changes of a Hastelloy alloy under 10 MeV electron irradiation at 650 °C for 700 h to a total fluence of 2 × 10– 3 dpa (displacements per atom) were investigated by transmission electron microscopy and by 3-dimensional atom-probe tomography utilizing a local-electrode atom-probe tomograph. Transmission electron microscopy analysis before irradiation reveals two types of precipitates: (i) spheroidal with a mean diameter of 22 nm; and (ii) ones with an irregular morphology of a few nm in diameter. The spheroidal precipitates (i) are coherent with the fcc matrix and their number density is ∼3 × 1021 m– 3. Electron diffraction patterns from these precipitates exhibit superlattice reflections corresponding to the L12 ordered structure. The chemical composition as measured by atom-probe tomography, is about 75 at.% Ni with additions of Al, Ti and Mo. The other type of precipitate (ii) is mainly enriched in Ni and Mo and its number density is ca. 3.6 × 1022 m– 3. The diffuse diffraction intensity maxima arising from these precipitates are observed at <1 1/2 0>fcc, which are attributed to compositional short-range order. After electron irradiation, the Ni – Al-rich precipitates (i) exhibiting L12 superlattice reflections have disappeared completely, while the diffuse intensity maxima from the Ni – Mo rich clusters (ii) are still visible. The results are discussed with respect to the influence of the electron irradiation on the morphology and structural changes of the ordered precipitates.
Investigation of surface film nanostructure and assessment of its impact on friction force stabilization during automotive braking
Authors: Österle Werner , Prietzel Claudia , Dmitriev Andrey Ivanovich 
Published: May 2010

Abstract
The unique nanostructure formed during severe as well as moderate braking on the surface of brake discs was investigated by conventional and analytical Transmission Electron Microscopy. In both cases nanocrystalline magnetite mixed with carbon nanoinclusions and minor amounts of other pad constituents were identified. On the basis of these observations the friction performance of a single micro-contact was simulated with the method of Movable Cellular Automata. Inspite of a simplified nanostructure which was examined in two dimensions only, the calculated mean coefficient of friction fitted well to the value usually demanded for automotive braking. Furthermore, the model predicts that oxide films without soft nanoinclusions are not capable of providing smooth velocity accommodation at the pad–disc interface and thus lead to unstable friction behaviour.
Creep strength of a binary Al62Ti38 alloy
Authors: Sturm Daniel , Heilmaier Martin , Saage Holger , Aguilar Julio , Schmitz Georg J. , Drevermann Anne , Palm Martin , Stein Frank , Engberding Nico , Kelm Klemens , Irsen Stephan 
Published: May 2010

Abstract
Al-rich Ti – Al alloys, as compared to Ti-rich -TiAl-based alloys, offer an additional reduction in density of 20 %, better oxidation resistance and sufficient strength at high temperatures. High temperature creep of a binary Al62Ti28 alloy was studied in compression in the temperature range between 1 173 K and 1 323 K in air. It is shown that the alloy exhibits quite reasonable creep resistance at 1 173 K, especially in view of its low density of around 3.8 g cm– 3. Stress exponents calculated as the slope n = log (strain rate)/ log (stress) = 4 were found to be relatively constant for the temperature and stress regime investigated. This indicates that dislocation climb may be the rate controlling creep mechanism. The values of the activation energies for creep for the as-cast and the annealed Al62Ti38 material coincides well with those found in the literature for interdiffusion of Al in -TiAl.
The joint properties of dissimilar aluminum plates joined by friction stir welding
Authors: Sarsilmaz Furkan , Çaydaş Ulaş , Hasçalik Ahmet , Tanriover Levent 
Published: May 2010

Abstract
Friction stir welding (FSW) can be used to join dissimilar Al alloys which have different mechanical properties without causing any weld zone defects under a wide range of welding conditions. In this study, AA2024 and AA5052 aluminum alloys were successfully joined together using FSW. FSW process parameters such as tool rotational speed and traverse speed were varied to explore their effects on the microstructural and mechanical properties of welded couples. Tension and fatigue tests were carried out and hardness measurements were conducted on cross-sections of the weld zones. Fatigue tests were performed using a fatigue test machine and the fatigue strength was analyzed by drawing S–N curves and critically observing fatigue fracture surfaces of the tested samples. The microstructures of the alloys and fracture surfaces were examined by optical and scanning electron microscopy. Experimental results indicate that microstructural and mechanical properties are significantly affected by changing welding parameters within the chosen range of conditions.
Human Tumor Antigen-Specific Helper and Regulatory T Cells Share Common Epitope Specificity but Exhibit Distinct T Cell Repertoire
Authors: Fourcade Julien , Sun Zhaojun , Kudela Pavol , Janjic Bratislav , Kirkwood John M. , El-Hafnawy Talal , Zarour Hassane M. 
Published: May 2010

Abstract
CD4+ regulatory T cells (Tregs) accumulate at tumor sites and play a critical role in the suppression of immune responses against tumor cells. In this study, we show that two immunodominant epitopes derived from the tumor Ags (TAs) NY-ESO-1 and TRAG-3 stimulate both CD4+ Th cells and Tregs. TA-specific Tregs inhibit the proliferation of allogenic T cells, act in a cell-to-cell contact dependent fashion and require activation to suppress IL-2 secretion by T cells. TRAG-3 and NY-ESO-1–specific Tregs exhibit either a Th1-, a Th2-, or a Th0-type cytokine profile and dot not produce IL-10 or TGF-β. The Foxp3 levels vary from one Treg clone to another and are significantly lower than those of CD4+CD25high Tregs. In contrast to NY-ESO-1–specific Th cells, the NY-ESO-1–specific and TRAG-3–specific Treg clonotypes share a common TCR CDR3 Vβ usage with Foxp3+CD4+CD25high and CD4+CD25− T cells and were not detectable in PBLs of other melanoma patients and of healthy donors, suggesting that their recruitment occurs through the peripheral conversion of CD4+CD25− T cells upon chronic Ag exposure. Collectively, our findings demonstrate that the same epitopes spontaneously stimulate both Th cells and Tregs in patients with advanced melanoma. They also suggest that TA-specific Treg expansion may be better impaired by therapies aimed at depleting CD4+CD25high Tregs and preventing the peripheral conversion of CD4+CD25− T cells.
Vasodilator-Stimulated Phosphoprotein Regulates Inside-Out Signaling of β2 Integrins in Neutrophils
Authors: Deevi Ravi K. , Koney-Dash Madhuri , Kissenpfennig Adrien , Johnston James A. , Schuh Kai , Walter Ulrich , Dib Karim 
Published: May 2010

AbstractThe monomeric GTPase Rap1 controls functional activation of β2 integrins in leukocytes. In this article, we describe a novel mechanism by which the chemoattractant fMLP activates Rap1 and inside-out signaling of β2 integrins. We found that fMLP-induced activation of Rap1 in human polymorphonuclear leukocytes or neutrophils and differentiated PLB-985 cells was blocked by inhibitors of the NO/guanosine-3′,5′-cyclic monophosphate–dependent protein kinase (cGKI) pathway [N-(3-(aminomethyl)benzyl)acetamidine, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, DT-3 peptide, 8-(4-chlorophenylthio)guanosine 3′,5′-cyclic monophosphothioate, Rp-isomer triethylammonium salt–guanosine-3′,5′-cyclic monophosphate], indicating that the downstream signaling events in Rap1 activation involve the production of NO and guanosine-3′,5′-cyclic monophosphate, as well as the activation of cGKI. Silencing the expression of vasodilator-stimulated phosphoprotein (VASP), a substrate of cGKI, in resting PLB-985 cells or mice neutrophils led to constitutive activation of Rap1. In parallel, silencing VASP in differentiated PLB-985 cells led to recruitment of C3G, a guanine nucleotide exchange factor for Rap1, to the plasma membrane. Expression of murine GFP-tagged phosphodeficient VASP Ser235Ala mutant (murine serine 235 of VASP corresponds to human serine 239) in PLB-985 cells blunted fMLP-induced translocation of C3G to the membrane and activation of Rap1. Thus, bacterial fMLP triggers cGKI-dependent phosphorylation of human VASP on serine 239 and, thereby, controls membrane recruitment of C3G, which is required for activation of Rap1 and β2 integrin-dependent antibacterial functions of neutrophils.
Injective Convolution Operators on ℓ∞(Γ) are Surjective
Authors: Choi Yemon 
Published: May 2010

AbstractLet Γ be a discrete group and let f ∈ ℓ1(Γ). We observe that if the natural convolution operator ρf : ℓ∞(Γ) → ℓ∞(Γ) is injective, then f is invertible in ℓ1(Γ). Our proof simplifies and generalizes calculations in a preprint of Deninger and Schmidt by appealing to the direct finiteness of the algebra ℓ1(Γ).We give simple examples to show that in general one cannot replace ℓ∞ with ℓp, 1 ≤ p < ∞, nor with L∞(G) for nondiscrete G. Finally, we consider the problem of extending the main result to the case of weighted convolution operators on Γ, and give some partial results.
Asymptotics of Perimeter-Minimizing Partitions
Authors: Maurmann Quinn , Engelstein Max , Marcuccio Anthony , Pritchard Taryn 
Published: May 2010

AbstractWe prove that the least perimeterP(n) of a partition of a smooth, compact Riemannian surface intonregions of equal areaAis asymptotic ton/2 times the perimeter of a planar regular hexagon of areaA. Along the way, we derive tighter estimates for flat tori, Klein bottles, truncated cylinders, and Möbius bands.
Functional Adhesive Surfaces with “Gecko” Effect: The Concept of Contact Splitting
Authors: Kamperman Marleen , Kroner Elmar , del Campo Aránzazu , McMeeking Robert M. , Arzt Eduard 
Published: May 2010

AbstractNature has developed reversibly adhesive surfaces whose stickiness has attracted much research attention over the last decade. The central lesson from nature is that “patterned” or “fibrillar” surfaces can produce higher adhesion forces to flat and rough substrates than smooth surfaces. This paper critically examines the principles behind fibrillar adhesion from a contact mechanics perspective, where much progress has been made in recent years. The benefits derived from “contact splitting” into fibrils are separated into extrinsic/intrinsic contributions from fibril deformation, adaptability to rough surfaces, size effects due to surface‐to‐volume ratio, uniformity of stress distribution, and defect‐controlled adhesion. Another section covers essential considerations for reliable and reproducible adhesion testing, where better standardization is still required. It is argued that, in view of the large number of parameters, a thorough understanding of adhesion effects is required to enable the fabrication of reliable adhesive surfaces based on biological examples.
Design of Multiresponsive Hydrogel Particles and Assemblies
Authors: Hendrickson Grant R. , Smith Michael H. , South Antoinette B. , Lyon L. Andrew 
Published: May 2010

AbstractIn the realm of soft nanotechnology, hydrogel micro‐ and nanoparticles represent a versatile class of responsive materials. Over the last decade, our group has investigated the synthesis and physicochemical properties of a variety of synthetic hydrogel particles. From these efforts, several particle types have emerged with potentially enabling features for biological applications, including nanogels for targeted drug delivery, microlenses for biosensing, and coatings for biomedical devices. For example, core/shell nanogels have been used to encapsulate and deliver small interfering RNA to ovarian cancer cells; nanogels used in this fashion may improve therapeutic outcomes for a variety of macromolecular therapeutics. Microgels arranged as multilayers on implantable biomaterials greatly minimize the host inflammatory response to the material. Furthermore, the triggered release of drugs (i.e., insulin) has been demonstrated from similar assemblies. The goal of this feature article is to highlight developments in the design of responsive microgels and nanogels in the context of our recent efforts and in relation to the community that has grown up around this fascinating class of materials.
Effect of Contact Mode on the Electrical Transport and Field‐Emission Performance of Individual Boron Nanowires
Authors: Liu Fei , Su Zanjia , Li Li , Mo Fuyao , Jin Shunyu , Deng Shaozhi , Chen Jun , Shen Chengmin , Gao Hongjun , Xu Ningsheng 
Published: May 2010

AbstractVapor–liquid–solid processing of boron nanowires (BNWs) can be carried out either using a bottom‐up or top‐down growth mode, which results in different contact modes between the nanowire and the substrate. The contact mode may strongly affect the electrical transport and field‐emission performance of the individual boron nanowires grown on a Si substrate. The electrical transport and field‐emission characteristics of individual boron nanowires of different contact modes are investigated in situ using a scanning electron microscope. The contact barriers are very distinct for the different contact modes. Moreover, the transition from a “contact‐limited” to a “bulk‐limited” field‐emission (FE) process is demonstrated in nanoemitters for the first time, and the proposed improved metal–insulator–vacuum (MIV) model may better illustrate the nonlinear behavior of the Fowler‐Nordheim (FN) plots in these nanoscale systems. Individual BNWs with different contact modes have a discrepancy in their emission stability and vacuum breakdown characteristics though they have similar aspect ratios, which suggests that their electrical transport and field‐emission performance are closely related to their contact mode. Boron nanowires grown in the base‐up mode have better field‐emission performances and are more beneficial than those grown in the top‐down mode for various device applications.
Induced SER‐Activity in Nanostructured Ag–Silica–Au Supports via Long‐Range Plasmon Coupling
Authors: Feng Jiu‐Ju , Gernert Ulrich , Hildebrandt Peter , Weidinger Inez M. 
Published: May 2010

AbstractA novel Ag–silica–Au hybrid device is developed that displays a long‐range plasmon transfer of Ag to Au leading to enhanced Raman scattering of molecules largely separated from the optically excited Ag surface. A nanoscopically rough Ag surface is coated by a silica spacer of variable thickness from ∼1 to 21 nm and a thin Au film of ∼25 nm thickness. The outer Au surface is further functionalized by a self‐assembled monolayer (SAM) for electrostatic binding of the heme protein cytochrome c (Cyt c) that serves as a Raman probe and model enzyme. High‐quality surface‐enhanced resonance Raman (SERR) spectra are obtained with 413 nm excitation, demonstrating that the enhancement results exclusively from excitation of Ag surface plasmons. The enhancement factor is estimated to be 2 × 104–8 × 103 for a separation of Cyt c from the Ag surface by 28–47 nm, corresponding to an attenuation of the enhancement by a factor of only 2–6 compared to Cyt c adsorbed directly on a SAM‐coated Ag electrode. Upon immobilization of Cyt c on the functionalized Ag–silica–Au device, the native structure and redox properties are preserved as demonstrated by time‐ and potential‐dependent SERR spectroscopy.
Ruthenium‐Catalyzed Alkyne Oxidation with Part‐Per‐Million Catalyst Loadings
Authors: Ren Wei , Liu Jinfeng , Chen Long , Wan Xiaobing 
Published: May 2010

AbstractUsing a catalytic system of the (cymene)ruthenium dichloride dimer, [Ru(cymene)Cl2]2, (0.001 mol%) and iodine (10 mol%), a variety of alkynes bearing different functional groups were oxidized with tert‐butyl hydroperoxide (TBHP; 70% solution in water) under mild conditions to give 1,2‐diketones in good to excellent yields. Two noteworthy features of the method are the extremely high catalyst productivity (TON up to 420,000) and scale‐up to 1 mol. Preliminary mechanism investigations showed that iodonium ion and water were involved in the transformation.
Sex differences in child nutritional and immunological status 5–9 years post contact in fringe highland Papua New Guinea
Authors: Decaro Jason A. , Decaro Erin , Worthman Carol M. 
Published: May 2010

AbstractObjectives:This study examines sex differences in vulnerability among children experiencing rapid culture change that may reflect distinct microecologies driven by differential parental investment and/or sex‐specific life history strategies. Apparent female growth canalization may be a life history strategy favoring growth over maintenance but also may reflect sex‐differentiated selection for resilience based on unequal treatment during early life.Methods:Stature, weight, and serum measures of C‐reactive protein (CRP, an inflammation marker) and Epstein‐Barr Virus antibodies (EBV, a humoral immune response marker) were collected longitudinally among children/adolescents ages 5–20 years (N= 65), 5–9 years after sustained contact in a fringe highland hunter‐horticulturalist group from the Schrader Range in Papua New Guinea exhibiting male preference and sex‐biased survival. It was hypothesized that girls would exhibit canalization, with better nutritional status than boys; lower maintenance investment would yield lower female immune activation; and because of differential survivorship, females would appear increasingly canalized as early conditions for girls worsened relative to boys.Results:Girls had greater arm circumferencez‐scores than boys, less frequent stunting, and lower CRP despite high pathogen load. Average nutritional status for girls improved over time as the sex ratio became increasingly male biased and the condition of female infants reportedly worsened.Conclusions:Both canalization and survivorship effects were found. Although a life history perspective on female canalization can help explain developmental outcomes in populations undergoing rapid culture change amid adversity, possible sex differences in the strength of survivorship effects that select for resiliency should not be ignored. Am. J. Hum. Biol. 22:657–666, 2010. © 2010 Wiley‐Liss, Inc.
Chronic radiation exposure in the Rivne‐Polissia region of Ukraine: Implications for birth defects
Authors: Dancause Kelsey Needham , Yevtushok Lyubov , Lapchenko Serhiy , Shumlyansky Ihor , Shevchenko Genadiy , Wertelecki Wladimir , Garruto Ralph M. 
Published: May 2010

AbstractObjectives:The health effects of chronic low‐dose radiation exposure remains a controversial question. Monitoring after the Chernobyl nuclear accident in Ukraine suggested that chronic low‐dose radiation exposure was not linked to cancer mortality among the general population. However, elevated rates of birth defects in contaminated compared to uncontaminated regions suggest that exposure to radiation in utero might impact development and that chronic radiation exposure might represent an underestimated risk to human health.Methods:We sought to determine current radiation exposure routes in Rivne‐Polissia, a region of Ukraine contaminated by the Chernobyl accident. This represents a first step toward comprehensive studies of the effects of chronic radiation exposure on human health. We designed and administered a dietary and activity survey to 344 women in Polissia. We assessed types and sources of food consumed, types of outdoor activities, and alcohol intake.Results:Alcohol intake was low and alone does not account for the observed high rates of birth defects. Wild foods, especially mushrooms and berries, and locally produced foods, especially milk related, were major radiation exposure routes. Additionally, women were exposed to radiation through inhalation while burning grasses and potato vines in fields, and wood for cooking and heating.Conclusions:Twenty four years after the Chernobyl accident, women continue to be chronically exposed to low‐dose radiation at levels exceeding current recommendations. This might contribute (especially synergistically with alcohol consumption and micronutrient deficiencies) to higher prevalence of birth defects in areas of Ukraine with high levels of radiation contamination compared to uncontaminated areas. Am. J. Hum. Biol. 22:667–674, 2010. © 2010 Wiley‐Liss, Inc.