bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cerebral edema following photodynamic therapy using endogenous and exogenous photosensitizers in normal brain
Authors: Mathews Marlon S. , Chighvinadze David , Gach H. Michael , Uzal Francisco A. , Madsen Steen J. , Hirschberg Henry 
Published: October 2011

AbstractBackground and ObjectiveFailure of treatment for high‐grade gliomas is usually due to local recurrence at the site of surgical resection indicating that a more aggressive form of local therapy such as photodynamic therapy (PDT) could be of benefit. The increase in brain edema following PDT using endogenous and exogenous photosensitizers was compared in terms of animal survival, MR imaging, and histopathological changes in normal brain.Materials and MethodsFischer rats were exposed to increasing laser light treatment following intraperitoneal injection of either the photosensitizers 5‐aminolevulinic acid (ALA) or aluminum phthalocyanine disulfonate (AlPcS2a). Light treatment was applied either via an optical fiber inserted directly into the brain parenchyma or through a fiber applied to the surface of the intact skull. Edema development was followed by T2‐weighted MR imaging.ResultsALA and AlPcS2a PDT resulted in a fluence dependent increase in cerebral edema and mortality. AlPcS2a PDT showed significant edema and mortality even at low fluences following interstitial light delivery, which was reduced with surface illumination. The mechanism of edema was determined to be vasogenic by response to steroid therapy and confirmed on histological images.ConclusionsT2 and contrast enhanced T1 MRI scanning proved to be a highly effective and noninvasive modality in following the development of the edema reaction and the degree and time course of blood–brain barrier dysfunction thus allowing the use of fewer animals. ALA mediated PDT induced a lower edema reaction than that observed with the photosensitizer AlPcS2a. Lasers Surg. Med. 43:892‐900, 2011. © 2011 Wiley Periodicals, Inc.
Copolymers: Efficient Carriers for Intelligent Nanoparticulate Drug Targeting and Gene Therapy
Authors: Hamidi Mehrdad , Shahbazi Mohammad‐Ali , Rostamizadeh Kobra 
Published: October 2011

AbstractCopolymers are among the most promising substances used in the preparation of drug/gene delivery systems. Different categories of copolymers, including block copolymers, graft copolymers, star copolymers and crosslinked copolymers, are of interest in drug delivery. A variety of nanostructures, including polymeric micelles, polymersomes and hydrogels, have been prepared from copolymers and tested successfully for their drug delivery potential. The most recent area of interest in this field is smart nanostructures, which benefit from the stimuli‐responsive properties of copolymeric moieties to achieve novel targeted drug delivery systems. Different copolymer applications in drug/gene delivery using nanotechnology‐based approaches with particular emphasis on smart nanoparticles are reviewed.magnified image
Microwave‐Assisted Derivatization of Cellulose, 2 – The Surprising Effect of the Structure of Ionic Liquids on the Dissolution and Acylation of the Biopolymer
Authors: El Seoud Omar A. , da Silva Valdinéia C. , Possidonio Shirley , Casarano Romeu , Arêas Elizabeth P. G. , Gimenes Paula 
Published: October 2011

AbstractThe relevance of the structure of ILs for the dissolution and microwave‐assisted acylation of eucalyptus cellulose is reported. The 1‐R‐3‐methylimizadolium‐X ILs with X = Cl, Ac and R = 1‐butyl, 2‐methoxyethyl, 1‐heptyl, and 3,6‐dioxa‐(1‐heptyl) are studied: C4MeImX, C3OMeImX, C7MeImX, and C5O2MeImX. The dissolution efficiencies are C3OMeImAc > C4MeImAc and C7MeImAc > C5O2MeImAc, i.e., they depend on the length of the side chain. This surprising result is corroborated by (i) cellulose acylation by ethanoic, butanoic, and hexanoic anhydride; (ii) the energy of viscous flow of the ILs; (iii) the solvatochromic properties of the ILs. Our results show that C3OMeImAc and C4MeImAc are distinct from C7MeImAc and C5O2MeImAc, due to chain‐dependent hydrogen bonding and hydrophobic interactions.
Poly(propylene) Nanocomposites Containing Various Carbon Nanostructures
Authors: Li Yunfeng , Zhu Jiahua , Wei Suying , Ryu Jongeun , Wang Qiang , Sun Luyi , Guo Zhanhu 
Published: October 2011

AbstractPP nanocomposites containing different carbon nanofillers (CNTs, CNFs, GnPs, CB) are fabricated and further processed by hot compression molding. A high level of nanofiller dispersion is found. The NCs exhibit improved thermal stability and higher crystallinity. Both electrical conductivity and real permittivity increase with increasing nanofiller loading. A strongly aspect ratio dependent electrical conductivity percolation is observed at loadings of 15.0, 12.0, 5.0, and 3.0 wt% for CB, GnPs, CNFs, and CNTs, respectively. The rheological behavior of the NC melts is also investigated. A small concentration of the nanofillers is found to affect the modulus and viscosity of the PP melts significantly.
Functional Degradable Polymers via Radical Ring‐Opening Polymerization and Click Chemistry
Authors: Maji Samarendra , Zheng Mengyao , Agarwal Seema 
Published: October 2011

AbstractThe use of free‐radical polymerization for the formation of an alkyne‐functionalized polymer with ester units of polycaprolactone type in the backbone is shown. This is done by the copolymerization of a cyclic ketene acetal [2‐methylene‐1,3‐dioxepane (MDO)] with propargyl acrylate using a free radical initiator, azobis(isobutyronitrile). Structural characterization of the copolymers using 1D and 2D NMR techniques shows the random distribution and very high percentage of inclusion of alkyne groups onto the polymer backbone. The exemplary grafting of a biocompatible polymer [poly(ethylene glycol)] via azide‐alkyne “click” chemistry is also shown. Hydrolytic degradation behavior and biocompatibility of the polymers (cytotoxicity) studies are also reported.
Reversible Photocycloadditions, a Powerful Tool for Tailoring (Nano)Materials
Authors: Cardenas‐Daw Carlos , Kroeger Anja , Schaertl Wolfgang , Froimowicz Pablo , Landfester Katharina 
Published: October 2011

AbstractMolecularly designed materials are increasingly attracting attention not only because of the variety of their applications but also due to the challenging strategies necessary for their design and synthesis. Highly complex and functional (nano)materials are obtained by exploiting simple tools and concepts from different disciplines, introducing the desired properties into the final product. It is shown that by combining fundaments from organic chemistry, polymer and materials science, photoresponsive nanoparticles are easily generated, and how responsiveness is achieved by exploiting photocycloadditions, which are extremely selective, react in good yields without the formation of side products, proceed under benign conditions, and present the great advantage of being reversible.
Diffusion and Reaction Phenomena in Solution‐Based Healing of Polymer Coatings Using the Diels–Alder Reaction
Authors: Pratama Purnomo A. , Peterson Amy M. , Palmese Giuseppe R. 
Published: October 2011

AbstractThe healing of a furan‐functional epoxy coating using bismaleimide (BMI) solutions is demonstrated. Corrosion studies of scratched coated carbon steel show that solution healing of damaged coatings inhibits corrosion. The healing relies on (i) the diffusion of solution components into the polymer, causing the system to swell, thus bringing crack surfaces into contact, and (ii) Diels–Alder adduct formation between furan moieties of the polymer network and the maleimide, resulting in covalent bonding across the crack interface. For the system investigated, crack healing is reaction‐limited for small crack widths. The results provide a guideline for the design and implementation of self‐healing systems based on BMI solution encapsulation.
Synthesis and Properties of Novel Thermoresponsive Polyesters with Oligo(ethylene glycol) Pendent Chains
Authors: Feng Lei , Liu Yu , Hao Jianyuan , Li Xiaohong , Xiong Chengdong , Deng Xianmo 
Published: October 2011

AbstractA new class of thermoresponsive polyesters is prepared by alternating ring‐opening copolymerization of succinic anhydride (SA) and epoxide bearing oligo(ethylene glycol) (oligo‐EG) pendant chains with the number of repeat ethylene glycol unit ranging from 1 to 3. The copolymerization kinetics and their various properties are investigated in detail. The increase of oligo‐EG length leads to a significant shift of the thermoresponsive transition to higher temperature. The copolymers hydrolyzed with unusual chain end cleavage mode and base acceleration feature. And the copolymers and their degradation products had no acute toxicities. The reported thermoresponsive polyesters are highly useful materials for in vivo biomedical applications.
Representation of Hydrogen Atoms in Molecular Dynamics Simulations: The Influence on the Computed Properties of Thin Polystyrene Films
Authors: Muntean Stela Andrea , Wedershoven Hubertus M. J. M. , Gerasimov Roman A. , Lyulin Alexey V. 
Published: October 2011

AbstractThe united atoms (UA) and dummy hydrogen atom (DHA) approaches for molecular dynamics simulations of the interface between oxidized atactic polystyrene (aPS) thin films and water are compared. For both oxidized and non‐oxidized aPS films the polymer density profile decays steepest when using the UA model. The surface roughness of the aPS film and the ordering of the phenyl rings near the surface decrease upon changing from vacuum to water for the UA, but not for the DHA model. This also supports the fact that the non‐oxidized aPS films modeled in DHA representation become less hydrophobic. The water structure close to the interface also suggests that the aPS films modeled using UA are more hydrophobic compared to the aPS films modeled with DHA in the phenyl rings.magnified image
Estimation of fatigue life for aluminium welded joints with the application of artificial neural networks
Authors: Karakas Ö. 
Published: October 2011

AbstractThe aim of this investigation was determining the fatigue behaviour of welded aluminium joints and so the appertaining SN‐lines by application of Artificial Neural Network (ANN) architectures. For this, fatigue data obtained with aluminium welded joints subjected to constant amplitude loading were used. The main benefit of ANN is the good description of the effects of different factors on fatigue life. The results determined by the ANN method for four aluminium alloys are displayed in scatter bands of SN‐lines. It is observed that the trained results are in good agreement with the tested data and enable the estimation of SN‐lines.
Microstructure based fatigue analysis of cast components under variable amplitude loading
Authors: Eufinger J. , Heinrietz A. , Bruder T. , Hanselka H. 
Published: October 2011

AbstractReliable numerical fatigue life analyses are becoming increasingly important given the need to reduce the time and costs for product development and the need to evaluate large and single components. Stress‐based approaches as well as the local strain approach and its fracture mechanics based extension (PJ model) are in use for that. Both the local strain approach and the PJ model require the supply of pure material data. This requirement for input data that are not component‐specific makes such approaches interesting for widespread application. The accuracy of numerical fatigue life analyses is an essential criterion for the acceptance and the spread in industrial application. In the local strain approach, accuracy is determined on one hand by the transferability of material data for the fatigue life analysis of components and on the other by the damage accumulation rule. In this paper, the local strain approach and the PJ model are used to analyse fatigue life under both constant and variable amplitude loading. These analyses are based on the experimental results obtained from tests of a commercial vehicle component made of nodular cast iron EN‐GJS‐400‐15. Aspects of transferability and damage accumulation are considered. Results obtained from using an elastic‐plastic fracture mechanics based approach to estimate a PSWT‐N curve, taken into account the inhomogeneities in the microstructure of the cast iron, are also presented.
Fatigue assessment of laserbeam‐welded aluminium joints under multiaxial loading
Authors: Wiebesiek J. , Zemke M. , Sonsino C. M. , Kaufmann H. 
Published: October 2011

AbstractThis paper presents the results and evaluation of the multiaxial fatigue behaviour of laserbeam‐welded overlapped tubular joints made from the artificially hardened aluminium alloy AlSi1MgMn T6 (EN AW 6082 T6) under multiaxial loadings with constant and variable amplitudes. Several fatigue test series under pure axial and pure torsional loadings as well as combined axial and torsional proportional and non‐proportional loadings have been carried out in the range of 2·104 to 2·107 cycles. The assessment of the investigated thin‐walled joints is based on a local notch stress concept. In this concept the fatigue critical area of the weld root is substituted by a fictitious notch radius rref = 0.05 mm. The equivalent stresses in the notch, considering especially the fatigue life reducing influence of non‐proportional loading in comparison to proportional loading, were calculated by a recently developed hypothesis, which is called the Stress Space Curve Hypothesis (SSCH). This hypothesis is based on the time evolution of the stress state during one load cycle. In addition, the fatigue strength evaluation of multiaxial spectrum loading was carried out using a modified Gough‐Pollard algorithm.
Multiaxial fatigue behaviour of a short‐fibre reinforced polyamide – experiments and calculations
Authors: Moosbrugger E. , DeMonte M. , Jaschek K. , Fleckenstein J. , Büter A. 
Published: October 2011

AbstractThis paper deals with the fatigue behaviour of a short fibre reinforced thermoplastic under multi‐axial cyclic stress. Based on experimental results on notched and plain specimens, limits of existing methods for the fatigue life estimation in the design process of components exposed to complex multi‐axial loads were investigated. During the manufacturing process of short fibre reinforced thermoplastic components, a moderately anisotropic behaviour in stiffness and strength arises. Because of the material's anisotropy, classical failure hypotheses for the assessment of multiaxial load cases do not apply. In this study, a fatigue failure hypothesis was implemented that assesses the stress components in accordance with the correlating fatigue strengths in the material coordinate system, considering potential interaction between the stress components. Striving for a verified multi‐usable fatigue life assessment method, multiaxial load cases were examined experimentally. The experimental results on unnotched and notched specimens and the fatigue life estimation on the basis of the Tsai‐Wu‐failure hypothesis will be presented.
New experimental methods for investigating variable amplitude loading effects in HCF and VHCF regimes
Authors: Wagener R. , Melz T. , Fischer C. , Matthias M. , Kaufmann H. 
Published: October 2011

AbstractFor the investigation of variable amplitude loading effects, it is necessary to increase the test frequency of conventional testing facilities because, for the evaluation of many components, test results with more than 107 cycles are also needed. However, due to the restriction of conventional testing facilities and the associated costs and required time, variable amplitude testing is almost limited to 107 cycles. Service loading with more than 107 cycles to failure is characterized by low amplitudes with a high number of cycles. The challenge in investigation of material fatigue in the regimes of high cycle and very high cycle fatigue is to apply this large number of cycles to failure in an acceptable time frame. For this reason, it is essential to use a machine, which is able to operate at high frequencies. In this paper, two testing machine concepts with piezo actuators are presented. In the first concept, a high performance piezo stack actuator is presented, in which the specimen and the load cell are mechanically assembled in series. This set‐up applies forces up to 10 kN and testing frequencies up to 1000 Hz. The second testing facility is a hybrid testing system, which consists of an inertial mass actuator and a servo hydraulic actuator connected in parallel. Both systems are capable of testing normal specimen dimensions and provide the possibility to work with variable amplitude loading as well as constant amplitude loading.
Design methods for reliable fatigue assessment of PM components
Authors: Baumgartner J. , Lipp K. , Bruder T. , Kaufmann H. 
Published: October 2011

AbstractThe use of PM materials is rapidly expanding with an increasing concentration on highly loaded structural parts such as synchroniser hubs, gears, sprockets or shifting forks. The successful implementation of PM materials for such parts depends on a reliable fatigue design concept. Such a design concept has to consider the local durability, especially in fatigue critical sharply notched areas, depending on the local density of the material and stress gradients. This paper summarises different design methods in order to transfer the fatigue behaviour of specimens to components by considering sharply notched areas. Four different local approaches have been investigated: the highly stressed volume approach, the stress gradient approach, the critical distance method and the stress averaging method according to Neuber. The design methods have been analysed on the basis of fatigue testing results of unnotched and notched fatigue specimens and of synchroniser hubs made from a 4% Ni diffusion‐alloyed steel material (Distaloy AE+0.6%C). The transferability of characteristic fatigue properties from specimens to a sharply notched component, a synchroniser hub, is presented and the practicability of the design methods demonstrated and discussed. These investigations showed that the most reliable concept was the highly stressed volume approach. The accuracy of the approach can be comprehended separating statistical and so called material support effect.
Aluminium alloys exposed to borderline solutions – a methodology to evaluate the susceptibility to corrosion fatigue with respect to corrosive de‐icers
Authors: Troßmann T. , Yu L. , Bauer K. , Kaufmann H. , Grimm J. 
Published: October 2011

AbstractIn addition to high mechanical loads certain components for the automotive industry are exposed to corrosive environments, especially during winter, when corrosion promoting de‐icers are essential to sustain road traffic. The underlying research work contributes to the evaluation of the corrosion fatigue performance of aluminium alloys relevant for automotive application generally, while the present text focuses on wrought alloys. Aluminium alloys are of special interest because of the opportunity to reduce expenses for an additional corrosion protection and to support lightweight construction of vehicles. Components exposed to simultaneous mechanical and corrosive service loads as well as corrosion tests of different scale level (immersion and cabinet testing, long term outdoor exposure of components, usage on test carriers) were analysed to evaluate typical forms of corrosion. Based upon the prevailing damaging mechanism of material conditions with known differences in susceptibility to specific forms of corrosion, like intergranular corrosion or pitting, methods were derived to evolve service relevant types of corrosion during laboratory tests.
Approaches to fatigue life assessment applied in the very high cycle regime
Authors: Pyttel B. , Berger C. , Schneider N. , Bruder T. , Eufinger J. 
Published: October 2011

AbstractDesigners and calculation engineers are becoming increasingly interested in the latest results on very high cycle fatigue (VHCF). Often, the influence of loading with a very high number of cycles on component behaviour is estimated conservatively, but the exact safety margin is unknown. This paper gives an overview of failure mechanisms in the HCF‐ and VHCF‐regions and of material and component related influences, which have to be considered in the fatigue life assessment. The state of the art of design codes, recommendations from the literature and initial investigations on variable amplitude loading in the VHCF‐regime are presented. This review indicates that further research activities are necessary to improve fatigue life assessment in order to allow a reduction of safety margins.
Transgenic insulin‐like growth factor‐1 stimulates activation of COX‐2 signaling in mammary glands
Authors: Tian Jie , Lambertz Isabel , Berton Thomas R. , Rundhaug Joyce E. , Kiguchi Kaoru , Shirley Stephanie H. , DiGiovanni John , Conti Claudio J. , Fischer Susan M. , Fuchs‐Young Robin 
Published: October 2011

AbstractStudies show that elevated insulin‐like growth factor‐1 (IGF‐1) levels are associated with an increased risk of breast cancer; however, mechanisms through which IGF‐1 promotes mammary tumorigenesis in vivo have not been fully elucidated. To assess the possible involvement of COX‐2 signaling in the pro‐tumorigenic effects of IGF‐1 in mammary glands, we used the unique BK5.IGF‐1 mouse model in which transgenic (Tg) mice have significantly increased incidence of spontaneous and DMBA‐induced mammary cancer compared to wild type (WT) littermates. Studies revealed that COX‐2 expression was significantly increased in Tg mammary glands and tumors, compared to age‐matched WTs. Consistent with this, PGE2 levels were also increased in Tg mammary glands. Analysis of expression of the EP receptors that mediate the effects of PGE2 showed that among the four G‐protein‐coupled receptors, EP3 expression was elevated in Tg glands. Up‐regulation of the COX‐2/PGE2/EP3 pathway was accompanied by increased expression of VEGF and a striking enhancement of angiogenesis in IGF‐1 Tg mammary glands. Treatment with celecoxib, a selective COX‐2 inhibitor, caused a 45% reduction in mammary PGE2 levels, attenuated the influx of mast cells and reduced vascularization in Tg glands. These findings indicate that the COX‐2/PGE2/EP3 signaling pathway is involved in IGF‐1‐stimulated mammary tumorigenesis and that COX‐2‐selective inhibitors may be useful in the prevention or treatment of breast cancer associated with elevated IGF‐1 levels in humans. © 2011 Wiley Periodicals, Inc.