bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrochromatography on acrylate‐based monolith in cyclic olefin copolymer microchip: A cost‐effective and easy‐to‐use technology
Authors: Ladner Yoann , Crétier Gérard , Faure Karine
Published: August 2012

This article shows that there is great interest in using an electrochromatographic microchip made of hexyl acrylate (HA) based porous monolith cast within the channel of a cyclic olefin copolymer (COC) device. The monolith is simultaneously in situ synthesized and anchored to the inner walls of the channel in less than 10 min. By appropriate choice of light intensity used during the synthesis, the separation efficiency obtained for nonpolar solutes such as polycyclic aromatic hydrocarbons (PAH) is increased up to 250 000 plates/m. The performance of this HA‐filled COC microchip was investigated for a wide range of analytes of varying nature. The reversed‐phase separation of four aflatoxins is obtained in less than 2 min. The baseline separation of a mixture of neurotransmitters including six amino acids and two catecholamines is possible thanks to the superimposition of the differences in electrophoretic mobility on the chromatographic process. The durability of the system at pH 13 allows the separation of five biogenic amines and the quantitative determination of two of them in numerous wine samples. The feasibility of on‐line preconcentration is also demonstrated. Hydrophilic surface modification of COC channel via UV‐photografting with poly(ethylene glycol) methacrylate (PEGMA) before in situ synthesis of HA, is necessary to reduce the adsorption of very hydrophobic solutes such as PAH during enrichment. The detection limit of fluoranthene is decreased down to less than 1 ppb with a preconcentration of 4.5 h on the HA‐filled PEGMA functionalized COC microchip.
Range imaging: a new method for high‐resolution topographic measurements in small‐ and medium‐scale field sites
Authors: Nitsche Manuel , Turowski Jens M. , Badoux Alexandre , Rickenmann Dieter , Kohoutek Tobias K. , Pauli Michael , Kirchner James W.
Published: August 2012

Topographic measurements are essential for the study of earth surface processes. Three‐dimensional data have been conventionally obtained through terrestrial laser scanning or photogrammetric methods. However, particularly in steep and rough terrain, high‐resolution field measurements remain challenging and often require new creative approaches. In this paper, range imaging is evaluated as an alternative method for obtaining surface data in such complex environments. Range imaging is an emerging time‐of‐flight technology, using phase shift measurements on a multi‐pixel sensor to generate a distance image of a surface. Its suitability for field measurements has yet not been tested. We found ambient light and surface reflectivity to be the main factors affecting error in distance measurements. Low‐reflectivity surfaces and strong illumination contrasts under direct exposure to sunlight lead to noisy distance measurements. However, regardless of lighting conditions, the accuracy of range imaging was markedly improved by averaging multiple images of the same scene. For medium ambient lighting (shade) and a light‐coloured surface the measurement uncertainty was approximately 9 mm. To further test the suitability of range imaging for field applications we measured a reach of a steep mountain stream with a horizontal resolution of approximately 1 cm (in the focal plane of the camera), allowing for the interpolation of a digital elevation model on a 2 cm grid. Comparison with an elevation model obtained from terrestrial laser scanning for the same site revealed that both models show similar degrees of topographic detail. Despite limitations in measurement range and accuracy, particularly at bright ambient lighting, range imaging offers three‐dimensional data in real time and video mode without the need of post‐processing. Therefore, range imaging is a useful complement or alternative to existing methods for high‐resolution measurements in small‐ to medium‐scale field sites. Copyright © 2012 John Wiley & Sons, Ltd.
Modulation of biocompatibility on poly(vinylidene fluoride) and polysulfone by oxygen plasma treatment and dopamine coating
Authors: Mangindaan Dave , Yared Ivan , Kurniawan Hengky , Sheu Joen‐Rong , Wang Meng‐Jiy
Published: September 2012

Poly(vinylidene fluoride) (PVDF) and polysulfone (PSf) are two polymers with excellent mechanical properties but insufficient biocompatibility mainly due to their surface hydrophobicity. This study has applied oxygen plasma treatments and dopamine coating on the two polymers and investigated the changes of the surface properties and interactions with mammalian cells. All modification steps were verified by means of Electron Spectroscopy for Chemical Analysis and contact angle measurements. Surface topology of materials and biomolecules was studied by atomic force measurements (AFM) and scanning electron microscopy (SEM). Protein adsorption was quantified by fluorescent imaging and Bradford method. The results showed that O2 plasma altered the surface hydrophilicity effectively on PSf and more than two folds of oxidation were obtained, when compared with the pristine one. The change of surface wettability was less significant on the O2 plasma treated PVDF due to less oxidation extent, which was identified by analyzing the chemical compositions. The provided functionalized PVDF and PSf surfaces were tested with bovine serum albumin and L‐929 mouse fibroblasts to evaluate the effects of surface modifications on protein adsorption and cell attachments. The biocompatibility was effectively promoted to fourfold and twofold on the hydrophobic PVDF and PSf by applying O2 plasma treatments within short treatment time. Moreover, the simple immobilization of polymers in dopamine solution resulted in hydrophilic surface coating with stability that caused threefold and twofold increases of biocompatibility on PVDF and PSf correspondingly. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 100A:3177–3188, 2012.
Strontium calcium phosphate for the repair of leporine (Oryctolagus cuniculus) ulna segmental defect
Authors: Mohan Beena G. , Shenoy Sachin J. , Babu Suresh S. , Varma H. K. , John Annie
Published: September 2012

Scaffolds to aid in repair, replacement, or regeneration of bony tissues have been developed using a wide spectra of materials. Under clinical conditions, assessment of healing and implant placement is guided radiographically. In this context, strontium's role in osteostimulation and its relevance in radio‐opacity are known. Therefore to aid in assessment and to ensure tissue regeneration, a bone mimetic porous strontium calcium phosphate (SrCaPO4) was synthesized in‐house, which was non‐cytotoxic (ISO 10993 (Part V) and subsequently characterized for its crystallinity, functional groups, and 3D porous topography. Furthermore, to assess the feasibility of the bioactive ceramic scaffolds in bone repair, SrCaPO4 and hydroxyapatite (HA—Control) scaffolds were implanted in the segmental ulna bone critical‐sized defect (1.5 cm) of New Zealand White Rabbits (leporine model—Oryctolagus cuniculus) for a period of 4 and 12 weeks, respectively. Healing of the defects was uneventful without any inflammation or infection. Radio‐opacity of SrCaPO4 within the defect site enabled easy assessment of implant placement and osteointegration. Again, histological evaluation coupled with micro‐CT and histomorphometrical analysis indicated that SrCaPO4 favored significant de novo bone formation in par with material degradation at 4 and 12 weeks post‐implantation compared to HA at 4 and 12 weeks. Investigations on this radio‐opaque SrCaPO4 established its role in the repair of critical‐sized segmental defects, proposing it as a suitable bone substitute for clinical reconstructive surgery with easy radiographic evaluation. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 101A:261–271, 2013.
Evaluation of hydrogels for bio‐printing applications
Authors: Murphy Sean V. , Skardal Aleksander , Atala Anthony
Published: September 2012

In the United States alone, there are approximately 500,000 burn injuries that require medical treatment every year. Limitations of current treatments necessitate the development of new methods that can be applied quicker, result in faster wound regeneration, and yield skin that is cosmetically similar to undamaged skin. The development of new hydrogel biomaterials and bioprinting deposition technologies has provided a platform to address this need. Herein we evaluated characteristics of twelve hydrogels to determine their suitability for bioprinting applications. We chose hydrogels that are either commercially available, or are commonly used for research purposes. We evaluated specific hydrogel properties relevant to bioprinting applications, specifically; gelation time, swelling or contraction, stability, biocompatibility and printability. Further, we described regulatory, commercial and financial aspects of each of the hydrogels. While many of the hydrogels screened may exhibit characteristics suitable for other applications, UV‐crosslinked Extracel, a hyaluronic acid‐based hydrogel, had many of the desired properties for our bioprinting application. Taken together with commercial availability, shelf life, potential for regulatory approval and ease of use, these materials hold the potential to be further developed into fast and effective wound healing treatments. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 101A:272–284, 2013.
Nucleation and growth of apatite on an anatase layer irradiated with UV light under different environmental conditions
Authors: Uetsuki Keita , Nakai Shinsuke , Shirosaki Yuki , Hayakawa Satoshi , Osaka Akiyoshi
Published: September 2012

Implant surfaces must sometimes be modified to form strong bonds to host tissues. The method of depositing an anatase layer on chemically pure titanium by chemical oxidation with H2O2 and subsequent calcination (CHT) is known to deposit apatite under physiological conditions; it thus exhibits bone‐bonding ability. UV irradiation should affect the bonding ability because the CHT anatase layer would experience certain chemical modifications, such as a decrease or an increase in the number of TiOH and TiO(H)Ti sites; these sites are considered active sites for apatite nucleation. When in vitro apatite deposition was examined, using Kokubo's simulated body fluid, UV irradiation in air reduced the apatite‐forming ability of the CHT anatase layer, and UV irradiation on the samples in water enhanced the ability. These results were correlated to changes in the TiOH and TiO(H)Ti sites, as determined by O 1s X‐ray photoelectron spectroscopy. Analysis of the number and size of the semi‐spherical apatite particles and their surface coverage led to a model: proper assembly of the TiOH and TiO(H)Ti sites should only give rise to the induction of apatite nucleation, analogous to topotaxy effects. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 101A: 712–719, 2013.
Wear particles promote endotoxin tolerance in macrophages by inducing interleukin‐1 receptor‐associated kinase‐M expression
Authors: Zhang Yangchun , Yu Shiming , Xiao Jianhong , Hou Changhe , Li Ziqing , Zhang Ziji , Zhai Qiyi , Lehto Matti , Konttinen Yrjö T. , Sheng Puyi
Published: September 2012

Toll‐like receptors (TLRs) recognizing pathogen‐associated molecular patterns (PAMP) play a role in local immunity and participate in implant‐associated loosening. TLRs‐mediated signaling is regulated by interleukin‐1 receptor‐associated kinase‐M (IRAK‐M). Our previous studies have proved that IRAK‐M is induced by wear particles in macrophages from periprosthetic tissues. In this study, the IRAK‐M‐related mechanisms were further explored by lipopolysaccharide (LPS) and/or titanium (Ti) particles stimulations and small interfering RNAs (siRNAs). The protein level of IRAK‐M was studied using western blotting and tumor necrosis factor‐α (TNF‐α), and interleukin‐1β (IL‐1β) levels were measured using ELISA. Results showed that in RAW264.7 cells stimulated by LPS after Ti particle pre‐exposure, IRAK‐M was slightly changed, compared with LPS stimulation. And levels of TNF‐α and IL‐1β in cultures stimulated by LPS first after Ti particle pre‐exposure were lower than in the other two groups which were stimulated by LPS with or without Ti particles (p < 0.001), whereas there were no statistic differences between the later two (p > 0.05). The cytokines were lowest in Ti particles alone stimulation. After siRNAs silenced, IRAK‐M‐deficient cells exhibited increased expression of the cytokines in LPS stimulation after Ti particle pre‐exposure and when stimulated with Ti particles alone. Our findings suggest that debris‐induced IRAK‐M decreases foreign body reactions, but at the same time, the over‐expression of IRAK‐M may also be detrimental on local intrusion of PAMPs or bacteria, negatively regulates the LPS‐induced and TLRs‐mediated inflammation and results in immunosuppression in periprosthetic tissue, which may predispose to implant‐associated infections. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 101A: 733–739, 2013.
Dopamine‐assisted immobilization of hydroxyapatite nanoparticles and RGD peptides to improve the osteoconductivity of titanium
Authors: Chien Chih‐Yuan , Liu Tse‐Ying , Kuo Wei‐Hsuan , Wang Meng‐Jiy , Tsai Wei‐Bor
Published: September 2012

Hydroxyapatite (HAp) coating on orthopedic implants is a common strategy to increase osteointegration. In this work, a facile deposition method based on dopamine polymerization was developed for preparation of HAp‐coated titanium substrates for orthopedic applications. Nanostructured HAp was mixed with an alkaline dopamine solution and then deposited onto titanium to form a dopamine/HAp ad‐layer. The deposition of dopamine/HAp greatly enhanced the adhesion, proliferation, and mineralization of osteoblasts. Furthermore, RGD‐containing peptides were immobilized to dopamine/HAp coated titanium and further enhanced cell adhesion and osteogenic differentiation. In conclusion, this facile dopamine‐assisted surface modification method shows a great potential for orthopedic and dental applications. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 101A: 740–747, 2013.
Subthalamic stimulation improves the cerebral hemodynamic response to the cold pressure test in patients with Parkinson's disease
Authors: Rätsep Tõnu , Asser Toomas
Published: September 2012

Purpose.

Disturbances of the autonomic nervous system are common in patients with Parkinson's disease (PD) but the effect of deep brain stimulation of the subthalamic nucleus on cerebrovascular reactivity is not entirely known.

Methods.

Seven patients in an advanced stage of the disease and seven healthy age‐matched controls participated in the study, which took place after one night of drug withdrawal. Cerebral blood flow velocity was continuously monitored on both sides with transcranial Doppler ultrasound, and cerebrovascular reactivity (CR) was evaluated with the cold pressure test. The measurements were repeated and compared during the stimulation‐on and ‐off phases.

Results.

The PD patients had significantly higher CR values in the stimulation‐on than ‐off conditions (15.1% ± 6.9 versus 9.4% ± 6.2; p = 0.03). CR values were higher in controls than in patients in the stimulation‐off condition (20.4% ± 12.5 versus 9.4% ± 6.2; p = 0.007) without a significant difference with the stimulation‐on phase.

Conclusions.

CR, evaluated by the response to the cold pressure test, is impaired in patients with advanced PD and improved by subthalamic nucleus. © 2012 Wiley Periodicals, Inc. J Clin Ultrasound, 2012.
Locally Symmetric Graphs of Girth 4
Authors: Perles Micha A. , Martini Horst , Kupitz Yaakov S.
Published: September 2012

We classify the family of connected, locally symmetric graphs of girth 4 (finite and infinite). They are all regular, with the exception of the complete bipartite graph . There are, up to isomorphism, exactly four such k‐regular graphs for every , one for , two for , and exactly three for every infinite cardinal k. In the last paragraph, we consider locally symmetric graphs of girth >4.
Reproducibility of 1H MR spectroscopy of hip bone marrow at 3 tesla
Authors: Pansini Vittorio M. , Monnet Aurélien , Salleron Julia , Penel Guillaume , Migaud Henry , Cotten Anne
Published: September 2012

Purpose:

To assess the reproducibility of fat content (FC) values in five different anatomical areas of proximal femur by the means of 1H 3 Tesla MR spectroscopy and to evaluate if any statistical difference exists when comparing right side to left side FC values in the same individual.

Materials and Methods:

Thirty‐three volunteers underwent unilateral 1H MR spectroscopy of the hip. From 1 to 4 weeks later, they repeat the MR examination of the same hip to assess the reproducibility of the technique. Fifteen other volunteers underwent a bilateral 1H MR hip spectroscopy to compare right and left side FC values.

Results:

The reproducibility of 1H MR spectroscopy was high in all the anatomic areas considered, ranging from 0.90 to 0.98. No statistically significant difference was found when the fat content values on the right side were compared to those on the left side. (P > 0.16).

Conclusion:

The 3 Tesla 1H MR spectroscopy of hip bone marrow permitted highly reproducible fat content values in all the five anatomic areas examined. No statistical significant difference existed when comparing fat content values of the right side to those of the left side in the same individual. J. Magn. Reson. Imaging 2012; 36:1445–1449. © 2012 Wiley Periodicals, Inc.
Optimizing lavage during knee arthroscopy: A three‐dimensional MRI study
Authors: Nord Russell M. , Badowski Natalie , Elkins Christopher , Alley Marcus , Harris Alex H.S , Dragoo Jason L.
Published: September 2012

Purpose:

To determine the best positioning and the resulting fluid flow patterns inside the knee during arthroscopy, reducing the surgical morbidity associated with the arthroscopic irrigation and debridement of a septic knee joint.

Materials and Methods:

Three‐dimensional MRI, using an MRI‐compatible human cadaveric knee arthroscopic model, generated fluid flow diagrams and velocity vector data. This was analyzed for six different arthroscopic configurations and at six different locations within the knee joint.

Results:

At any one static arthroscopic position, fluid flow velocity differed at the various locations in the knee, often with statistically significantly greater flow at one location over another. In general, flow was greatest at the location at which the inflow cannula terminated and preferentially flowed directly to the outflow cannula location, neglecting spaces in the knee that were not on this direct path. Three‐portal arthroscopy provided no benefit over two‐portal arthroscopy.

Conclusion:

To maximize arthroscopic lavage throughout all compartments in the knee, the arthroscopist must individually enter each space in the knee. Static arthroscopy in the setting of knee sepsis may lead to inadequate flow in certain areas of the knee and may lead to treatment failure. Three‐portal arthroscopy does not improve lavage efficiency. J. Magn. Reson. Imaging 2013;37:201–207. © 2012 Wiley Periodicals, Inc.
Mechanism of intraseasonal oceanic signature in the region off southern tip of India during boreal summer
Authors: Jayakumar A. , Gnanaseelan C. , Sabin T. P.
Published: September 2012

Sea surface temperature (SST) in the region off southern tip of India (STI, 75–83°E, 5–8°N) exhibited a prominent variability in the intraseasonal time scale (both 30–90 d and 10–30 d band) during boreal summer. Mechanisms associated with this intraseasonal variability are studied using three‐dimensional ocean general circulation model (OGCM) sensitivity experiments, satellite observed outgoing longwave radiation, SST and winds for the period 1998–2007. The background oceanic structure of the STI characterized by a shallow thermocline and moderate mixed layer provided ideal conditions for strong oceanic sub‐surface processes. The model mixed layer heat budget reveals that the oceanic processes such as horizontal advection and vertical processes are the dominant mechanisms in the STI region as compared with air‐sea flux. Sensitivity experiments with the OGCM reveals that the ocean dynamical processes contribute to most of the intraseasonal SST variability and the wind stress contributes to 85% of the variability whereas surface flux contributes to only 15% for the 30–90 d SST variability. Higher amplitude of surface flux perturbation and its contribution to SST in the 10–30 d as compared with the 30–90 d band are evident in the model experiment and are consistent with the observational analysis. There is year‐to‐year variability in the relative role of horizontal and vertical processes for different intraseasonal SST events over STI.
Flooding of the continental shelves as a contributor to deglacial CH4 rise
Authors: Ridgwell Andy , Maslin Mark , Kaplan Jed O.
Published: August 2012

The transition from the last glacial and beginning of Bølling–Allerød and Pre‐Boreal periods in particular is marked by rapid increases in atmospheric methane (CH4) concentrations. The CH4 concentrations reached during these intervals, ∼650–750 ppb, is twice that at the last glacial maximum and is not exceeded until the onset of industrialization at the end of the Holocene. Periods of rapid sea‐level rise as the Last Glacial Maximum ice sheets retreated and associated with ‘melt‐water pulses’ appear to coincide with the onset of elevated concentrations of CH4, suggestive of a potential causative link. Here we identify and outline a mechanism involving the flooding of the continental shelves that were exposed and vegetated during the glacial sea‐level low stand and that can help account for some of these observations. Specifically, we hypothesize that waterlogging (and later, flooding) of large tracts of forest and savanna in the Tropics and Subtropics during the deglacial transition and early Holocene would have resulted in rapid anaerobic decomposition of standing biomass and emission of methane to the atmosphere. This novel mechanism, akin to the consequences of filling new hydroelectric reservoirs, provides a mechanistic explanation for the apparent synchronicity between rate of sea‐level rise and occurrence of elevated concentrations of ice core CH4. However, shelf flooding and the creation of transient wetlands are unlikely to explain more than ∼60 ppb of the increase in atmospheric CH4 during the deglacial transition, requiring additional mechanisms to explain the bulk of the glacial to interglacial increase. Similarly, this mechanism has the potential also to play some role in the rapid changes in atmospheric methane associated with the Dansgaard–Oeschger cycles. Copyright © 2012 John Wiley & Sons, Ltd.
SERS detection of red organic dyes in Ag‐agar gel
Authors: Lofrumento Cristiana , Ricci Marilena , Platania Elena , Becucci Maurizio , Castellucci Emilio
Published: September 2012

Micro‐Raman spectroscopy has been widely employed in the last few years for the study of artworks, allowing for the characterization of a high class of pictorial materials. However, the detection of organic dyes by conventional Raman spectroscopy is quite difficult, due to the high fluorescence provided by these compounds. Recently, remarkable improvements have been achieved by the introduction of the surface enhanced Raman spectroscopy (SERS) technique for the analysis of organic dyes.

In the present work, a new method is presented, based on the use of a SERS probe made of agar‐agar coupled with silver nanoparticles, for a non‐destructive and minimally invasive micro‐extraction of dyes from textiles. Ag‐agar gel has been tested first on textile mock‐ups dyed with alizarin, purpurin and carminic acid. SERS measurements have been performed adopting laser light excitations at 514.5 and 785 nm of a micro‐Raman setup. Highly structured SERS band intensities have been obtained. After having verified the safety of the method by colorimetric, X‐ray fluorescence and attenuated total reflectance Fourier transform infrared techniques, a real case, a pre‐Columbian piece of textile, have been investigated by Ag‐agar gel. This cutting‐edge method offers new possibilities for a sensitive and non‐destructive analysis of fluorescent materials. Copyright © 2012 John Wiley & Sons, Ltd.
Micro‐Raman analysis and finite‐element modeling of 3 C‐SiC microstructures
Authors: Piluso N. , Anzalone R. , Camarda M. , Severino A. , La Magna A. , D'Arrigo G. , La Via F.
Published: September 2012

Micro‐ and nano‐electromechanical systems (MEMS and NEMS) fabricated in 3 C‐SiC are receiving particular attention thanks to the material physical properties: its wide band gap (2.3 eV), its ability to operate at high temperatures, its mechanical strength and its inertness to the exposure in corrosive environments. However, high residual stress (which is normally generated during the hetero‐epitaxial growth process) makes the use of 3 C‐SiC in Si‐based MEMS fabrication techniques very limited leading to a failure of micro‐machined/sensor structures.

In this paper, micro‐Raman characterizations and finite‐element modeling (FEM) of microstructures realized on poly and single‐crystal (100) 3 C‐SiC/Si films are performed. Transverse optical (TO) Raman mode analysis reveals the stress relaxation on the free standing structure (796.5 cm−1) respect to the stressed unreleased region (795.7 cm−1). Also, microstructures as cantilever, bridge and planar rotating probe show an intense stress field located around the undercut region. Here, the TO Raman mode undergoes an intense shift, up to 2 cm−1, ascribed to the modification of the Raman stress tensor. Indeed, the generalized axial regime, described by diagonal components of the Raman stress tensor, cannot be applied in this region. Raman maps analysis and FEM simulations show the ‘activation’ of the shear stress, i.e. non‐diagonal components of the stress tensor. The stress‐Raman modes shift correlation, in the case of fully non‐diagonal stress tensors, has been investigated. The aim of future works will be to minimize the stress field generation and the defects density within the epitaxial layer. Copyright © 2012 John Wiley & Sons, Ltd.
Bioinspired Microorigami by Self‐Folding Polymer Films
Authors: Ionov Leonid
Published: August 2012

Investigation of self‐folding thin films, which mimic natural mechanisms of movement and form complex 3D structures, is a novel and very promising research direction. This manuscript summarizes recent advances in the development and application of biomimetic self‐folding polymer films.

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A Fast Method to Compute the MSD and MWD of Polymer Populations Formed by Step‐Growth Polymerization of Polyfunctional Monomers Bearing A and B Coreactive Groups
Authors: Hillegers L. Tom , Blokhuis Aart , Slot Johan J. M.
Published: September 2012

General step‐growth polymerization systems of order 2 are considered, i.e., systems of type “AfiBgi”, and a fast algorithmic method is presented to compute, at a given degree of conversion, the MSD and the MWD. The complete distribution is calculated; not just statistical averages of the polymer population such as $\overline {M} _{{\rm n}} $ or $\overline {M} _{{\rm w}} $. For the computation of the low‐ and intermediate size/weight parts of the distribution curves, a set of recurrence relations is used. The high‐molecular size/weight parts of the curves (right tails) are computed using an accurate approximation derived from generating functions. In a previous paper, we applied our method to general order‐1 systems, i.e., systems of type “Afi”.

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Influence of 1,5‐naphthalenediamine on thermomechanical properties of epoxy/copolyethersulphone blends
Authors: Cicala G. , Blanco I. , Latteri A. , Oliveri L. , Recca A.
Published: August 2012

The use of 1,5‐naphthalenediamine (ND) as curing agents for epoxy blends was studied. The epoxy monomer was a standard diglycidyl ether of bisphenol A while as modifier a laboratory made copolyethersulphone (coPES) was considered. The coPES was added at three percentages: 10, 20, and 30% wt. The stiff structure of ND increased both viscosity and glass transition temperature of the blends. The blends cured by ND showed higher viscosity compared to resins cured by 3,3′‐diammino diphenylsulfone or 4,4′‐methylenebis(2,6‐diethylaniline). Blends with higher coPES content (20 and 30% wt) showed viscosity fluctuation suggesting phase separation initiation but the combination of high viscosity and reactivity hindered the demixing process. This effect resulted in single glass transition for all formulations confirming the absence of phase separation. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Study of rheological, thermal, and mechanical behavior of reprocessed polyamide 6
Authors: Crespo J.E. , Parres F. , Peydró M.A. , Navarro R.
Published: August 2012

The effect of reprocessing Polyamide 6 (PA6) has been studied in this article. To simulate recycled PA, we reprocessed virgin PA through five cycles. The PA 6 has undergone mechanical, thermal and rheological characterization after the various cycles of reprocessing in order to evaluate the corresponding properties and correlate them with the number of cycles undergone. In order to widen our injection simulation analysis by computer (CAE: Computer Aided Engineering) of these new materials, it was necessary to determine the viscosity using a mathematical model; in this case the Cross‐WLF, to determine the relevant parameters. Our results show that tensile strength, elongation at break and hardness remain practically constant, while the charpy impact decreases as the number of reprocessing cycles increases. The effects of reprocessing on the material may decrease the rheological properties; specifically the viscosity of the material decreases with increasing processing cycles. The thermal properties are also influenced with the reprocessed material. The crystallinity increases and the degradation reaction will be advanced to increase the reprocessing cycle. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Dielectric behavior of aluminum hydroxide‐filled oil‐extended ethylene‐propylene‐diene‐monomer rubber composites in microwave fields
Authors: Nair Ajalesh Balachandran , Kalappura Ullas G. , Kurian Philip , Joseph Rani
Published: September 2012

Oil‐extended ethylene‐propylene‐diene rubber composites were prepared with aluminum hydroxide (ATH) and high abrasion furnace carbon black. The dielectric properties at microwave frequencies of the samples were measured in the S (2–4 GHz) band using cavity perturbation technique. The thermal stability of the composites was studied using thermogravimetric analysis. The morphology of the composites was investigated by scanning electron microscopic studies. The fire retardancy of the composites was identified through the limiting oxygen index and horizontal burning test (UL94 HB). The dielectric permittivity, AC conductivity, and absorption coefficient of the highly ATH loaded systems are much greater than the unfilled and lower systems. At higher loading, the dielectric heating coefficient and skin depth were found to decrease significantly. The incorporation of ATH was found to improve the thermal stability and flame retardancy of EPDM. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Practical considerations in the determination of compound‐specific amino acid δ15N values in animal and plant tissues by gas chromatography‐combustion‐isotope ratio mass spectrometry, following derivatisation to their N‐acetylisopropyl esters
Authors: Styring Amy K. , Kuhl Alison , Knowles Timothy D. J. , Fraser Rebecca A. , Bogaard Amy , Evershed Richard P.
Published: September 2012

RATIONALE

Stable nitrogen isotope (δ15N) values of bone collagen are routinely used to inform interpretations of diet and trophic positions within contemporary and ancient ecosystems, yet the underlying physiological and biochemical factors which contribute to the bulk collagen δ15N value remain little understood. Determination of individual amino acid (AA) δ15N values in animal and plant proteins can help to elucidate the cycling of nitrogen and inform predictions of palaeodiet and ecology.

METHODS

In this study we present a methodology for the measurement of amino acid δ15N values using gas chromatography‐combustion‐isotope ratio mass spectrometry (GC‐C‐IRMS). Amino acid standards of known δ15N values were derivatised to their N‐acetylisopropyl (NAIP) esters and purified through Dowex ion‐exchange resin to determine any isotopic fractionation associated with derivatisation and ion‐exchange chromatography. The effect of starch on AA δ15N values was also determined by hydrolysing bone collagen with and without the presence of starch.

RESULTS

The amino acids derivatised to their NAIP esters give values within ±0.8‰ of their δ15N values measured separately by elemental analyser (EA)‐IRMS, with a precision of better than 0.8‰. The δ15N values of AAs after Dowex ion‐exchange chromatography were within ±0.9‰ of their values prior to ion‐exchange chromatography. The AA δ15N values of bone collagen hydrolysed with and without starch were within ±0.8‰.

CONCLUSIONS

Hydrolysis of lipid‐extracted plant material followed by purification of AAs using Dowex ion‐exchange resin and derivatisation to their NAIP esters is a suitable protocol for the accurate determination of individual plant and animal AA δ15N values by GC‐C‐IRMS. Copyright © 2012 John Wiley & Sons, Ltd.
High molecular weight non‐polar hydrocarbons as pure model substances and in motor oil samples can be ionized without fragmentation by atmospheric pressure chemical ionization mass spectrometry
Authors: Hourani Nadim , Kuhnert Nikolai
Published: September 2012

RATIONALE

High molecular weight non‐polar hydrocarbons are still difficult to detect by mass spectrometry. Although several studies have targeted this problem, lack of good self‐ionization has limited the ability of mass spectrometry to examine these hydrocarbons. Failure to control ion generation in the atmospheric pressure chemical ionization (APCI) source hampers the detection of intact stable gas‐phase ions of non‐polar hydrocarbon in mass spectrometry.

METHODS

Seventeen non‐volatile non‐polar hydrocarbons, reported to be difficult to ionize, were examined by an optimized APCI methodology using nitrogen as the reagent gas.

RESULTS

All these analytes were successfully ionized as abundant and intact stable [M–H]+ ions without the use of any derivatization or adduct chemistry and without significant fragmentation. Application of the method to real‐life hydrocarbon mixtures like light shredder waste and car motor oil was demonstrated.

CONCLUSIONS

Despite numerous reports to the contrary, it is possible to ionize high molecular weight non‐polar hydrocarbons by APCI, omitting the use of additives. This finding represents a significant step towards extending the applicability of mass spectrometry to non‐polar hydrocarbon analyses in crude oil, petrochemical products, waste or food. Copyright © 2012 John Wiley & Sons, Ltd.
Surfactant self‐assembling in the gas phase: bis(2‐ethylhexyl)‐sulfosuccinate divalent metal ion anionic aggregates
Authors: Giorgi Gianluca , Ceraulo Leopoldo , Liveri Vincenzo Turco
Published: September 2012

RATIONALE

Investigation of fundamental aspects driving surfactant self‐assembling and of the capability of including guest molecules or ions in their micellar aggregates is an exciting research field for theoretical and technological reasons. In this light, assembling and chelating properties of sodium bis(2‐ethylhexyl)sulfosuccinate (AOTNa) towards divalent metal ion chlorides have been investigated in the gas phase by electrospray ionization mass spectrometry in negative ion mode, tandem mass spectrometry and energy‐resolved mass spectrometry.

METHODS

Water/methanol solutions of AOTNa and chloride salts of nickel, magnesium, calcium and manganese, with different AOTNa/metal salt ratios, were infused into the electrospray source of a LCQ DECA ion trap mass spectrometer, operating in negative ion mode, at a flow rate of 5 μL/min. Low energy collision‐induced dissociations were carried out by using helium with collision energy in the range 1–5 eV.

RESULTS

A variety of negatively singly charged monometallated and mixed metal aggregates have been observed, some of which were able to incorporate the metal counter ion of the inorganic salt used. The stability of these aggregates was evaluated by energy‐resolved mass spectrometry which showed, for the anions [AOTMIICl2]–, a stability order Ca > Mn > Mg > Ni. Their decomposition pathways show the unusual formation of the radical anions [C4HO6SMIICl]–•.

CONCLUSIONS

This study shed some light on the assembling and chelating properties of AOT– towards divalent metal ions to form negatively charged assemblies, some of them incorporating the metal counter ion of the inorganic salt used. Differently from what was observed with positively charged AOT‐MII aggregates, solvated species were not detectable. An exception to the even‐electron rule was observed in the decomposition pathway of [AOTMIICl2]–. Copyright © 2012 John Wiley & Sons, Ltd.
Quantification of cardiolipin molecular species in Escherichia coli lipid extracts using liquid chromatography/electrospray ionization mass spectrometry
Authors: Garrett Teresa A. , O'Neill Ashley C. , Hopson Marquise L.
Published: September 2012

RATIONALE

Cardiolipin (CL), a glycerophospholipid containing four acyl chains, is found in most organisms including Gram‐negative bacteria such as Escherichia coli. While CL composes only a fraction of the total glycerophospholipids, the four acyl chains lead to a large number of possible molecular species as defined by the total number of carbons and unsaturations in the acyl chains. Understanding the molecular composition of CL, and how it changes under different growth conditions, will aid in understanding the complex role of CL in E. coli.

METHODS

Normal‐phase liquid chromatography/electrospray ionization mass spectrometry was used to quantify the CL molecular species (as defined by the total number of carbons:unsaturations in the acyl chains) in lipid extracts prepared from E. coli grown at 15 °C, 30 °C, 37 °C and 42 °C.

RESULTS

Fifty‐six different CL species were identified as [M–2H]2– ions in E. coli lipid extracts ranging from 60:0 to 72:4. CL species with an increased total number of unsaturations were more abundant in lipid extracts prepared from cells grown at 15 °C as compared to higher temperatures.

CONCLUSIONS

This work characterizes the CL composition of E. coli cells grown at various temperatures. By quantifying CL species at a molecular level we have illuminated the molecular complexity of the CL in this relatively simple model organism. This data will be useful for understanding CL function in E. coli and other organisms. Copyright © 2012 John Wiley & Sons, Ltd.
On the temperature dependence of the shear viscosity and holography
Authors: Cremonini Sera , Gürsoy Umut , Szepietowski Phillip
Published: September 2012

Abstract

We examine the structure of the shear viscosity to entropy density ratio
$ \frac{\eta }{s} $
in holographic theories of gravity coupled to a scalar field, in the presence of higher derivative corrections. Thanks to a non-trivial scalar field profile,
$ \frac{\eta }{s} $
in this setup generically runs as a function of temperature. In particular, its temperature behavior is dictated by the shape of the scalar potential and of the scalar couplings to the higher derivative terms. We consider a number of dilatonic setups, but focus mostly on phenomenological models that are QCD-like. We determine the geometric conditions needed to identify local and global minima for
$ \frac{\eta }{s} $
as a function of temperature, which translate to restrictions on the signs and ranges of the higher derivative couplings. Finally, such restrictions lead to an holographic argument for the existence of a global minimum for
$ \frac{\eta }{s} $
in these models, at or above the deconfinement transition.
Impact of Posttransplantation Glomerulonephritis on Long‐term Outcome of Kidney Transplants: Single‐Center 20‐Year Experience
Authors: Yu Tung‐Min , Wen Mei‐Chin , Wu Ming‐Ju , Chen Cheng‐Hsu , Cheng Chi‐Hung , Li Chi‐Yuan , Shu Kuo‐Hsiung
Published: September 2012

Background

Successful renal transplantation has been performed in patients with end‐stage renal disease and has been routine in patients with end‐stage renal failure for more than two decades. Despite advances in the use of immunosuppressants, there has been only modest improvement in long‐term allograft survival. Accumulating data have demonstrated that chronic rejection and recurrent glomerulonephritis are major causes of long‐term allograft loss. However, data regarding the long‐term impact of posttransplantation glomerulonephritis (PTGN) on ethnic Chinese populations are still unavailable.

Methods

From 1984 to 2010, a total of 268 patients who underwent renal allograft biopsies were reviewed retrospectively. Renal outcomes were compared by Kaplan–Meier analysis, and risk factors for renal survival and all‐cause mortality were analyzed using the Cox proportional hazards model.

Results

In all, 85 patients (31.7 %) had PTGN, and the mean time of disease onset was 5.32 ± 5.18 years after transplantation. Among the 85 PTGN cases, 33 (39 %) were immunoglobulin A (IgA) nephropathy, 24 (28 %) were focal segmental glomerulosclerosis, and 8 (9.4 %) were membranous GN. Significant risk was associated with posttransplant IgA GN in hepatitis B virus carriers (odds ratio 5.371, 95 % confidence interval 1.68, 17.19; p = 0.0064). A total of 45 PTGN patients had allograft loss, of whom 49 % had IgA nephropathy. Patients with PTGN had inferior allograft survival rates compared to those with other pathologic findings (p < 0.0003).

Conclusions

Taken together, our results indicate that PTGN had a strong negative impact on long‐term kidney graft survival. Posttransplant IgA nephropathy is a leading cause of allograft loss in Chinese kidney transplant patients with PTGN.
Dynamics of phase fronts in magmagenic fluid in the formation of gold and silver deposits in Southern Kamchatka
Authors: Sharapov V.N. , Lapukhov A.S. , Guzman B.V. , Cherepanova V.K.
Published: September 2012

The origin of gold and silver deposits in the Southern Kamchatka ore district is considered in terms of a quantitative model of the dynamics of volcanogenic orthomagmatic fluid systems (VOFSs). This model takes into account structural, fluid dynamic, and thermophysical features of phase evolution in hydrothermal fluid systems differing in geometry and structural conditions of the discharge on the surfaces of volcanic edifices. It is shown that VOFSs forming sulfide-rich gold and silver deposits have no stationary impermeable caps in their discharge areas. Rather, for the most part, narrow regions of junction of phase fronts form in their interiors and migrate to the surface of volcanic edifices.

Three geothermal system types are predicted by the example of plane and conical fluid conductance zones with a cap horizon: (I) where the shallow decompression boiling zone does not arise at all because of large lateral heat loss, (II) where subsurface decompression boiling zones appear at the beginning of the heat wave formation and then such a zone is practically confined to the cap rocks, and (III) where a quasistationary decompression boiling zone forms after an initial instability period or approach to a thermal equilibrium. Fluctuations or oscillations of decompression boiling zone fronts within a range of depths can exist in type III systems.
Neotectonics and paleoseismicity of the lower Katun’ valley (Gorny Altai)
Authors: Deev E.V. , Zolnikov I.D. , Borodovsky A.P. , Goltsova S.V.
Published: September 2012

The lower Katun’ area has a complex neotectonic framework, with the largest fault zone of Katun’ consisting of several en-echelon graben segments. Late Pleistocene sediments that fill the Katun’ Fault bear signature of earthquake-induced soft-sediment deformation (seismites). Deformation due to seismic triggers can be discriminated from nonseismic one on the basis of special features and be related to prehistoric earthquakes according to a number of criteria. The observed deformation inside and outside burial mounds of the Chultukov Log-1 group may result from an earthquake that occurred in the end of the first millennium BC. Fault scarps in Late Pleistocene sediments, as well as deformed Iron Age tomb patterns, indicate that the Katun’ lower reaches can have experienced past earthquakes of intensity at least 5 or 6 and magnitudes from 4.5 to 6.0.
Current radiation environment in the Central Ecological Zone of the Baikal Natural Territory
Authors: Chernyago B.P. , Nepomnyashchikh A.I. , Medvedev V.I.
Published: September 2012

The main natural and human-induced radiation factors were assessed on the basis of long-term targeted radioecological studies in the Central Ecological Zone of the Baikal Natural Territory as a world heritage site. We identified areas with a problematic level of different radiation parameters determining the current radiation environment. Such areas should be taken into account in the development and implementation of nature management plans in the Baikal region, including ecotourism.
The critical layer in linear-shear boundary layers over acoustic linings
Authors: Brambley E. J. , Darau M. , Rienstra S. W.
Published: August 2012

Acoustics within mean flows are governed by the linearized Euler equations, which possess a singularity wherever the local mean flow velocity is equal to the phase speed of the disturbance. Such locations are termed critical layers, and are usually ignored when estimating the sound field, with their contribution assumed to be negligible. This paper studies fully both numerically and analytically a simple yet typical sheared ducted flow in order to investigate the influence of the critical layer, and shows that the neglect of critical layers is sometimes, but certainly not always, justified. The model is that of a linear-then-constant velocity profile with uniform density in a cylindrical duct, allowing exact Green’s function solutions in terms of Bessel functions and Frobenius expansions. For sources outside the sheared flow, the contribution of the critical layer is found to decay algebraically along the duct as $O(1/ {x}^{4} )$, where $x$ is the distance downstream of the source. For sources within the sheared flow, the contribution from the critical layer is found to consist of a non-modal disturbance of constant amplitude and a disturbance decaying algebraically as $O(1/ {x}^{3} )$. For thin boundary layers, these disturbances trigger the inherent convective instability of the flow. Extra care is required for high frequencies as the critical layer can be neglected only in combination with a particular downstream pole. The advantages of Frobenius expansions over direct numerical calculation are also demonstrated, especially with regard to spurious modes around the critical layer.