bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative mass spectrometry to investigate epidermal growth factor receptor phosphorylation dynamics
Authors: Schuchardt Sven , Borlak Jürgen
Published: November 2007

Identifying proteins of signaling networks has received much attention, because an array of biological processes are entirely dependent on protein cross‐talk and protein–protein interactions. Protein posttranslational modifications (PTM) add an additional layer of complexity, resulting in complex signaling networks. Of particular interest to our working group are the signaling networks of epidermal growth factor (EGF) receptor, a transmembrane receptor tyrosine kinase involved in various cellular processes, including cell proliferation, differentiation, and survival. Ligand binding to the N‐terminal residue of the extracellular domain of EGF receptor induces conformational changes, dimerization, and (auto)‐phosphorylation of intracellular tyrosine residues. In addition, activated EGF receptor may positively affect survival pathways, and thus determines the pathways for tumor growth and progression. Notably, in many human malignancies exaggerated EGF receptor activities are commonly observed. An understanding of the mechanism that results in aberrant phosphorylation of EGF receptor tyrosine residues and derived signaling cascades is crucial for an understanding of molecular mechanisms in cancer development. Here, we summarize recent labeling methods and discuss the difficulties in quantitative MS‐based phosphorylation assays to probe for receptor tyrosine kinase (RTK) activity. We also review recent advances in sample preparation to investigate membrane‐bound RTKs, MS‐based detection of phosphopeptides, and the diligent use of different quantitative methods for protein labeling. © 2007 Wiley Periodicals, Inc., Mass Spec Rev 27:51–65, 2008
Structure and Mechanical Properties of Chitosan/Poly(Vinyl Alcohol) Blend Films
Authors: Nakano Yumiko , Bin Yuezhen , Bando Mami , Nakashima Teruo , Okuno Tsumuko , Kurosu Hiromichi , Matsuo Masaru
Published: November 2007

Summary: The origins of the thermal and mechanical properties of chitosan and poly(vinyl alcohol) (PVA) with inter‐ and intra‐hydrogen bonds were investigated systematically by using X‐ray, DSC, positron annihilation and viscoelastic measurements. Based on their individual properties, the characteristics of the blend films were estimated in relation to their morphology and mechanical properties as a function of chitosan content. The characteristics of the blend films were also analyzed in terms of the deviation from a simple additive rule of chitosan and PVA content. These results suggested that the miscibility of chitosan and PVA could be ensured by entanglement of the amorphous chain segments of chitosan and PVA. Further detailed analysis revealed that the chitosan content on the film surface is higher than that of the admixture content of chitosan after elongation, although the chitosan and PVA chains were crystallized independently. The elongation could be achieved for the blend films whose PVA content was higher than 50% and the drawn blend films were transparent. Thus, it may be expected that sufficiently entangled meshes formed between chitosan and PVA amorphous chains within the film, the PVA content being higher than 50%, were maintained under the elongation process.
Effect of EPDM on Morphology, Mechanical Properties, Crystallization Behavior and Viscoelastic Properties of iPP+HDPE Blends
Authors: Vranjes Nina , Rek Vesna
Published: November 2007

Summary: Blends of isotactic polypropylene (iPP) and high density polyethylene (HDPE) with and without ethylene‐propylene‐diene (EPDM) terpolymer as compatibilizer were systematically investigated to determine the influence of the EPDM on blends properties. The morphology was studied by Scanning Electron Microscopy (SEM). Mechanical properties of investigated systems: tensile strength at break, elongation at break, yield stress and Izod impact strength were determined. Crystallization behavior was determined by Differential Scanning Calorimetry (DSC). Dynamic Mechanical Analysis (DMA) was used to determined the storage modulus (E′), loss modulus (E″), and loss tangent (tan δ). The PP+HDPE blend revealed poor adhesion between PP and HDPE phases. Finer morphology was obtained by EPDM addition in PP+HDPE blends and better interfacial adhesion. Addition of HDPE to PP decreased tensile strength at break, elongation and yield stress. Decrease of tensile strength and yield stress is faster with EPDM addition in PP+HDPE blends. Elongation at break and impact strength was significantly increased with EPDM addition. The addition of EPDM in PP+HDPE blends did not significantly change melting points of PP phase, while melting points of HDPE phase was slightly decreased in PP+HDPE+EPDM blends. The EPDM addition increased the percentage of crystallization (Xc) of PP in PP+HDPE blends. The increase of Xc of HDPE was found in the blend with HDPE as matrix. Dynamical mechanical analysis showed glass transitions of PP and HDPE phase, as well as the relaxation transitions of their crystalline phase. By addition of EPDM glass transitions (Tg) of HDPE and PP phases in PP+HDPE blends decreased. Storage modulus (E′) vs. temperatures (T) curves are in the region between E′/T curves of neat PP and HDPE. The decrease of E′ values at 25 °C with EPDM addition in PP+HDPE blends is more pronounced.
Band Broadening Function in Size Exclusion Chromatography of Polymers: Review of Some Recent Developments
Authors: Meira Gregorio , Netopilík Miloš , Potschka Martin , Schnöll‐Bitai Irene , Vega Jorge
Published: November 2007

Summary: This article reviews some recent developments on the determination of the Band Broadening Function (BBF) in Size Exclusion Chromatography (SEC) of polymers. It was carried out in the frame of the IUPAC Project: “Data Treatment in Size Exclusion Chromatography of Polymers”. The correction for band broadening (BB) is important for quantitative determinations of the molar mass distribution (MMD) of narrow‐distributed (or highly multimodal) polymers, and of derived variables such as kinetic parameters. In the narrow range of a molar mass standard, the BBF is uniform and of positive skewness. In a broad chromatographic range, the BBF is non‐uniform and skewed; and it can be adequately represented by an exponentially‐modified Gaussian function (EMG) of 2 parameters that vary slightly with elution volume: an increasing Gaussian variance and a decreasing exponential decay. Additionally, the total BBF variance remains almost constant if not close to the total exclusion limit. The following methods for determining BBF parameters are reviewed: a) a direct method based on assuming Poisson‐distributed MMDs; b) a direct method based on measuring the mass‐ and molar mass chromatograms of narrow standards; c) a theoretical method based on a stochastic model that is equivalent to the Giddings‐Eyring model; and d) a theoretical method based on a deterministic model obtained through an extension of the classical van Deemter expression. Ideally, the correction for BB requires a robust numerical inversion algorithm. However, alternative simplified solutions are also possible.
Macromol. Theory Simul. 9/2007
Authors: Guo Xiaohu , Pinna Marco , Zvelindovsky Andrei V.
Published: November 2007

Cover: A parallel, spatial decomposition based algorithm for large‐scale cell dynamics simulation is proposed. The numerical results show that the proposed parallel algorithm can provide an efficient way for computer simulation of block copolymers systems of experimental size. Further details can be found in the article by X. Guo, M. Pinna, and A. V. Zvelindovsky* on page 779.
The hp‐version of the BEM with quasi‐uniform meshes for a three‐dimensional crack problem: The case of a smooth crack having smooth boundary curve
Authors: Bespalov Alexei
Published: November 2007

The article considers a three‐dimensional crack problem in linear elasticity with Dirichlet boundary conditions. The crack in this model problem is assumed to be a smooth open surface with smooth boundary curve. The hp‐version of the boundary element method with weakly singular operator is applied to approximate the unknown jump of the traction which is not L2‐regular due to strong edge singularities. Assuming quasi‐uniform meshes and uniform distributions of polynomial degrees, we prove an a priori error estimate in the energy norm. The estimate gives an upper bound for the error in terms of the mesh size h and the polynomial degree p. It is optimal in h for any given data and quasi‐optimal in p for sufficiently smooth data. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2008
A photochemical method for immobilization of azidated dextran onto aminated poly(ethylene terephthalate) surfaces
Authors: Bhat Venugopal T , James Nirmala R , Jayakrishnan Athipettah
Published: November 2007

BACKGROUND: Dextran, a bacterial polysaccharide, has been reported to be as good as poly(ethylene glycol) in its protein‐rejecting and cell‐repelling abilities. In addition, the multivalent nature of dextran is advantageous for surface grafting of biologically active molecules. We report here a method to photochemically bind dextran hydrogel films to aminated poly(ethylene terephthalate) (PET) surfaces in aqueous media using a heterobifunctional crosslinker, 4‐azidobenzoic acid. In order to achieve this, dextran was first functionalized with the crosslinker using carbodiimide chemistry followed by photo‐crosslinking and immobilization onto the nucleophile‐rich aminated PET surfaces.

RESULTS: The presence of the immobilized dextran on PET was verified by attenuated total‐reflection Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, scanning electron microscopy and contact angle measurements. The grafted surface was highly hydrophilic due to the heavily hydrated polysaccharide network on the surface as demonstrated by the near zero water contact angle.

CONCLUSION: A photochemical method for surface immobilization of dextran onto aminated PET using aryl azide chemistry is a facile technique to generate highly hydrophilic and more hemocompatible surfaces. The aryl nitrenes generated by photolysis produce a metastable, electron‐deficient intermediate, azacycloheptatetraene, which is believed to be responsible for the simultaneous crosslinking of dextran and its immobilization onto the aminated PET surface. The aryl azide chemistry reported here for dextran could be useful as a versatile technique for surface modification of other nucleophile‐rich polymers to create dextran‐ or similar polysaccharide‐immobilized surfaces. Copyright © 2007 Society of Chemical Industry
Novel amphiphilic triblocks fitted with photocrosslinkable termini, and their photocrosslinking to conetworks
Authors: Chen Yaohong , Kennedy J. P.
Published: November 2007

Two new telechelic amphiphilic triblock copolymers, HE3‐PEG‐b‐PDMS‐b‐PEG‐HE3 and HE3‐PEG‐b‐PDMS‐b‐PEG‐HE3, i.e., sequence‐reversed triblocks of hydrophilic poly(ethylene glycol) (PEG) and hydrophobic polydimethylsiloxane (PDMS) segments fitted with photocrosslinkable tri[2‐(3,4‐cyclohexane oxide)ethyl‐dimethylsiloxy]silane (HE3) termini, were synthesized, characterized, photocrosslinked to amphiphilic conetworks (APCNs), and the properties of the APCNs were analyzed. APCNs in which the crosslinking sites are located in the hydrophobic domains exhibited significantly better mechanical properties than those in which the crosslinks were in the hydrophilic domains. The stiff domains formed of the UV‐crosslinkable HE3 chain‐end substituents provide not only crosslinking but reinforcement as well. The crosslinking/reinforcement efficiency was greatly enhanced by the addition of excess HE3. Water‐swollen APCNs were optically clear and exhibited mechanical properties appropriate for biomedical application. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 174–185, 2008
Thermodynamic cloud point assays
Authors: Bergbreiter David E. , Fu Hui
Published: November 2007

Analysis of cloud points and clouding curves by varying heating rates using a commercially available automated melting point apparatus is a method to obtain a corrected cloud point for polymers that have a lower critical solution temperature (LCST). Such assays also provide information about the effects of varying heating rates on LCSTs and similar stimuli‐responsive phase separation behavior. This melting point apparatus makes it experimentally simple to conduct such assays that probe the effect of varying heating rates, the effect of polymer structure, and the effect of solution components on the breadth and progress of the phase transition process over a wide temperature range. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 186–193, 2008
Non‐Axial Stress State in a Model Silo Generated by Eccentric Filling and Internal Inserts
Authors: Molenda Marek , Montross Michael D. , Horabik Józef
Published: November 2007

Dangerous nonuniformity of grain loads within a silo may be caused by eccentric discharge, eccentric loading, eccentric structural members fastened to the wall, geometrical imperfections or nonuniformity of the frictional conditions. Some of these effects have been quantified based on testing corrugated‐walled, flat floor model silos filled with wheat. In this type of silo, filling above a height to diameter ratio of H/D = 2.0 resulted in mixed flow (following the terminology of Eurocode 1) where grain slides along the wall during discharge above the effective transition and remains stagnant below the effective transition – located at H/D = ca. 0.7 (more details in [1]).

The degree of load asymmetry due to eccentric filling is demonstrated and compared to the worst case observed, i.e., eccentric discharge through an orifice located at a distance of 0.7 of the floor radius from the silo centerline. The presence of a nonsymmetric flow obstruction on the silo wall is found to cause dangerous local loads similar to eccentric discharge. Considerable nonuniformity in the load is observed during testing of a cylindrical obstruction immersed in grain supported on the silo floor with its axis parallel to the silo centerline. The mechanisms of these phenomena are still poorly understood, and a satisfactory theoretical description cannot be given.
Preliminary Experimental Analysis of a Spiral Jet Mill Performance
Authors: Katz Avi , Kalman Haim
Published: November 2007

Jet mills are common devices used in industry for the fine milling of dry particulate materials. The size reduction is caused by repeated impaction events between particles. Although many parameters affect the performance of a jet‐mill, only a few of them have been investigated by researchers to date. Furthermore, the published investigations test only a few materials. In order to bridge the knowledge gaps which exist, a new experimental apparatus was designed and constructed to enable experiments involving as many influencing parameters as possible. The new apparatus enables changing of the material feeding, mass flow rate, air flow rate, nozzle parameters (velocity, diameter, angle, number and shape), grinding chamber height and the classifier orientation. In this paper, preliminary experimental results concerning a number of the aforementioned parameters and their effect on the mill performance are presented.
Loads on Support Structural Elements Buried in Stockpiles
Authors: Roberts Alan W.
Published: November 2007

The paper presents a theory, combined with design equations, to compute the loads on structural elements, such as conveyor trestle legs or support columns buried in bulk solid storage systems such as stock piles. The stress conditions in the stored bulk solid in the immediate region of the buried structural element are shown to be a combination of active and passive stress states which are dependent on the method of filling and reclaim employed and the flow properties of the bulk solid. The theory examines the various loading conditions focusing on the determination of the lateral or bending load distribution as well as the compressive, in‐plane shear traction loads which may influence the buckling effect in buried structural support columns. The paper is illustrated by reference to a case study involving vertical support columns in a large bulk fertilizer shed. Experimental results performed on a small scale model of the bulk fertilizer facility are shown to confirm the predicted results.
On choosing the right ether for peptide precipitation after acid cleavage
Authors: de La Torre Beatriz G. , Andreu David
Published: November 2007

Methyl tert‐butyl ether (MTBE) and diethyl ether (DEE) tend to be regarded as interchangeable for the ‘cold ether’ workup concluding the final acidolytic cleavage and deprotection step of solid‐phase peptide syntheses. However, the use of MTBE to precipitate peptides from strong acid solutions is shown to give rise to t‐butyl alkylation byproducts, readily detectable by MALDI‐TOF MS. The problem can attain undesirable dimensions in the cleavage of peptide resins containing high proportions of aromatic residues, particularly in peptide nucleic acid (PNA) syntheses. In those cases, DEE workup is advisable, as it consistently leads to cleaner products. Copyright © 2007 European Peptide Society and John Wiley & Sons, Ltd.
Detection, characterization, and quantification of resveratrol glycosides in transgenic arabidopsis over‐expressing a sorghum stilbene synthase gene by liquid chromatography/tandem mass spectrometry
Authors: Lo Clive , Le Blanc J. C. Yves , Yu Christine K. Y. , Sze K. H. , Ng Dominic C. M. , Chu Ivan K.
Published: November 2007

Transgenic Arabidopsis plants were analyzed by liquid chromatography/tandem mass spectrometry (LC/MS/MS) to investigate the glycosylation patterns of resveratrol derived from expression of a sorghum stilbene synthase gene. In negative ionization mode, the different resveratrol derivatives fragmented to yield the diagnostic deprotonated resveratrol ion at m/z 227.2. The use of precursor ion scanning led to the identification of precursor ions for different resveratrol glycosides through rapid differentiation from other phytochemical constituents. Structural information was generated simultaneously from the low‐collision‐energy product ion spectra using hybrid linear ion‐trap mass spectrometry. Three additional resveratrol‐related metabolites – a resveratrol diglucoside (M1) and trans‐ and cis‐resveratrol acetylhexosides (M2 and M3) – were detected in the crude plant extracts. The identities of M1, M2, and M3 were confirmed by accurate mass analysis on a quadrupole time‐of‐flight mass spectrometer as well as β‐glucosidase digestion or UV‐induced isomerization. Quantitative analyses by LC/MS in multiple reaction monitoring mode revealed that resveratrol diglucoside and cis‐resveratrol acetyhexoside accumulated up to 2.79 and 10.38 µg/g, respectively, while trans‐resveratrol acetylhexoside was barely detectable. This study demonstrated the power of the hybrid linear ion‐trap technology for simultaneous profiling and structural characterization of stilbene‐related metabolites, which would be useful to understand how resveratrol is modified in sorghum and other plants. Copyright © 2007 John Wiley & Sons, Ltd.
Feasibility Study of Safe Breast Conservation in Large and Locally Advanced Cancers with Use of Radiopaque Markers to Mark Pre‐Neoadjuvant Chemotherapy Tumor Margins
Authors: Aggarwal Vivek , Agarwal Gaurav , Lal Punita , Krishnani Narendra , Mishra Anjali , Verma Ashok K. , Mishra Saroj K.
Published: November 2007

Background

The lack of objective documentation of pre‐neoadjuvant chemotherapy (NACT) margins after chemotherapy is a major constraint in performing safe breast‐conserving surgery (BCS) in patients with locally advanced breast cancer (LABC). Using a novel method of marking pre‐NACT tumor margins with indigenous silver wire markers, this prospective pilot study attempted to assess the feasibility of safe BCS in LABC patients by performing excision wide of the marked pre‐NACT margins.

Methods

LABC patients had sterile silver wire markers placed at all tumor margins percutaneously. Patients were then treated with NACT followed by wide local excision (WLE) incorporating pre‐NACT margins (ex vivo on mastectomy specimen or in vivo in patients opting for BCS). The histology of the margins wide of the post‐WLE cavity (pre‐NACT) and post‐NACT tumor was used to assess adequate disease clearance and safety of BCS.

Results

Altogether, 40 stage III breast cancer patients (mean tumor size 7.9 cm) were studied; none had marker‐related complications. Following NACT, the tumor size assessed by markers showed average regression by 1.5 cm. The pre‐NACT margins were histologically negative in 95% of the surgical specimens. In 2 (5%) patients both pre‐NACT and post‐NACT margins were positive; post‐NACT margins were infiltrated in 14 (35%).

Conclusions

The post‐NACT WLE that is wide of the marked pre‐NACT margins can achieve uninfiltrated margins in 95% of cases. If post‐NACT margins are used to guide the WLE, 35% patients would have infiltrated margins, some of which would remain undetected, putting patients at high risk of local recurrence. This novel indigenous method of identifying tumor margins with sterile silver wire markers is safe, inexpensive, practical, and effective; and it may help perform safe BCS in a large proportion of LABC patients.
The Other Side of the Coin: Perceived Positive Effects of Illness in Women Following Acute Myocardial Infarction
Authors: Norekvål Tone M. , Moons Philip , Hanestad Berit R. , Nordrehaug Jan E. , Wentzel-Larsen Tore , Fridlund Bengt
Published: November 2007

Background: Although myocardial infarction (MI) is linked with both physical and psychological impairments, the possibility of patients also experiencing positive outcomes of MI has received far less attention in research and in clinical practice. In particular, this aspect has been under-investigated in older persons and in women.

Aim: The purpose of this study was to investigate possible positive effects of illness, describe the patient characteristics and explore the nature and frequency of these effects in older women after MI.

Methods: A cross-sectional postal survey was conducted in 145 women aged 62–80 years, three months to five years after MI. Self-reported socio-demographic and clinical data, in addition to data from medical records, were collected. A single-item question – “All in all, was there anything positive about experiencing an MI?” – was used to assess positive effects of illness, in addition to an open-ended question on the nature of possible positive effects.

Results: A majority of the women (65%) reported positive effects from their MI experience. The women perceiving positive effects did not differ from those who did not on socio-demographic and clinical variables, except for being older ( p = 0.007) and less often readmitted ( p = 0.029). The groups did not differ significantly as to disease severity and time since MI. Four themes emerged from the open-ended questioning on the nature of perceived positive effects of the illness: Appreciating Life (55%), Getting Health Care (42%), Making Lifestyle Changes (36%), and Taking More Care of Self and Others (29%).

Conclusions: The findings contribute to a more complete picture of psychosocial issues in women after MI by providing evidence that positive effects are often experienced despite physical limitations. Nurses may use this knowledge as a tool in patient education and communication, although further research is needed to determine the most optimal interventions for MI patients.
INTENDING, FORESEEING, AND THE STATE
Authors: Enoch David
Published: November 2007

For many years, moral philosophers have been debating the conceptual and moral status of the distinction between intending harm and (merely) foreseeing harm. In this paper, after surveying some of the objections to the moral significance of this distinction in general, I focus on the special case of state action, arguing that whatever reasons we have to be suspicious about the distinction's moral significance in general, we have very good reasons to believe it lacks intrinsic moral significance when applied to state action. After arguing for this claim, I pursue in a preliminary way some of its implications.
How widespread and important is N2 fixation in the North Atlantic Ocean?
Authors: Reynolds Sarah E. , Mather Rhiannon L. , Wolff George A. , Williams Richard G. , Landolfi Angela , Sanders Richard , Woodward E. Malcolm S.
Published: November 2007

The spatial extent of N2 fixation in the Atlantic Ocean is examined by determining the isotopic composition of N in suspended particulate organic nitrogen (δ15N PONsusp). The samples were collected from zonal and meridional transects of the Atlantic Ocean during a 3‐year period. There is a consistent depleted δ15N PONsusp signal extending over the center of the northern subtropical gyre, which partly coincides with a region where the tracer N* increases westward following the gyre circulation. This nonconservative behavior of N* implies that N2 fixation is responsible for the depleted δ15N PONsusp. A mixing model suggests that N2 fixation over parts of the northern gyre provides up to 74% of the N utilized by phytoplankton. However, since the PONsusp represents only a small fraction of the total N pool, N2 fixation probably only plays a minor role in supplying new N to the euphotic zone in the surface waters of the northern subtropical gyre.
Climate and floods still govern California levee breaks
Authors: Florsheim J. L. , Dettinger M. D.
Published: November 2007

Even in heavily engineered river systems, climate still governs flood variability and thus still drives many levee breaks and geomorphic changes. We assemble a 155‐year record of levee breaks for a major California river system to find that breaks occurred in 25% of years during the 20th Century. A relation between levee breaks and river discharge is present that sets a discharge threshold above which most levee breaks occurred. That threshold corresponds to small floods with recurrence intervals of ∼2–3 years. Statistical analysis illustrates that levee breaks and peak discharges cycle (broadly) on a 12–15 year time scale, in time with warm‐wet storm patterns in California, but more slowly or more quickly than ENSO and PDO climate phenomena, respectively. Notably, these variations and thresholds persist through the 20th Century, suggesting that historical flood‐control effects have not reduced the occurrence or frequency of levee breaks.
Identification of an oxidative refolding intermediate of recombinant consensus interferon from inclusion bodies and design of a two‐stage strategy to promote correct disulfide‐bond formation
Authors: Liu Yong‐Dong , Zhang Gui‐Feng , Li Jing‐Jing , Chen Jing , Wang Yin‐Jue , Ding Hong , Su Zhi‐Guo
Published: November 2007

Dilution refolding of recombinant consensus IFN (interferon) from inclusion bodies suffers from low yield. A stable intermediate was found to mix with the correct product and to have an antiviral activity of less than 10% of the latter. This intermediate would form precipitates upon removal of the precipitation inhibitor arginine. Compared with the native protein, the intermediate moved more slowly on non‐reducing SDS/PAGE. The CD and fluorescence spectra indicated that it had formed a native‐like structure, but had only one disulfide bond: Cys29–Cys139. Further evidence showed that the formation of Cys29–Cys139 is specific and very likely to happen, even in the presence of a high concentration of reducing agent, whereas pairing of the other disulfide (Cys1–Cys99) needed a stronger oxidative condition. It competed with intermolecular disulfide bonding to form covalent oligomers. On the basis of this discovery, a two‐stage refolding step strategy was designed that employed a modified dilution refolding step followed by a dialysis refolding step. The first stage used a high concentration of reducing agent together with the precipitation inhibitor arginine. The purpose was to hinder any reaction through Cys1 or Cys99 but allow the intramolecular disulfide bonding of Cys29–Cys139. The second stage was a dialysis step that gradually increased the oxidative agent concentration and simultaneously decreased the arginine concentration. The refolding yield was increased from 35 to 82%, while the mass recovery was increased from 60 to 96%. Moreover, this strategy could suppress precipitation even after arginine was completely removed.
Coupling between surface plasmons via thermal emission of a dielectric layer sandwiched between two metal periodic layers
Authors: Tsai Ming-Wei , Chen Chia-Yi , Jiang Yu-Wei , Ye Yi-Han , Chang Hsu-Yu , Chuang Tzu-Hung , Lee Si-Chen
Published: November 2007

Metal/SiO2/metal trilayer thermally generated infrared emitters with different top and bottom periodic metal arrangements were fabricated and their emission spectra were measured. The coupling mechanisms of surface plasmon polaritons at top and bottom periodic metal structures were characterized. It is found that the top surface plasmon converted to light radiation directly, whereas the bottom surface plasmon can radiate out when its emission peak position matches that of the top surface plasmon. This opens the way to fabricate the high temperature operated, narrow bandwidth, and multiwavelength infrared light source.
Spin solitons in magnetized pair plasmas
Authors: Brodin G. , Marklund M.
Published: November 2007

A set of fluid equations, taking into account the spin properties of the electrons and positrons in a magnetoplasma, are derived. The magnetohydrodynamic limit of the pair plasma is investigated. It is shown that the microscopic spin properties of the electrons and positrons can lead to interesting macroscopic and collective effects in strongly magnetized plasmas. In particular, it is found that new Alfvénic solitary structures, governed by a modified Korteweg–de Vries equation, are allowed in such plasmas. These solitary structures vanish if the quantum spin effects are neglected. Our results should be of relevance for astrophysical plasmas, e.g., in pulsar magnetospheres, as well as for low-temperature laboratory plasmas.
Coaxial helicity injection in open-flux low-aspect-ratio toroidal discharges
Authors: Redd A. J. , Jarboe T. R. , Nelson B. A. , O’Neill R. G. , Smith R. J.
Published: November 2007

Open-flux low-aspect-ratio toroidal discharges generated and sustained by coaxial helicity injection (CHI) in the Helicity Injected Torus device (HIT-II) are described. The discharges in this study are flux tubes directly connected to the CHI electrodes, with poloidal flux less than or equal to the CHI injector flux, and no possibility of a significant closed-flux plasma core. Theoretically derived scalings for the dependence of CHI injector current on the toroidal field current and magnitude of the injector flux are experimentally confirmed, and empirical models are developed for the poloidal magnetic field and toroidal plasma current in open-flux discharges. In particular, the toroidal plasma current is independent of the toroidal magnetic field, both theoretically and empirically. Variations in injector flux geometry demonstrate that the CHI injector current leaves the electrode surfaces at the flux strike points, and that the relative width of the CHI injector determines whether the dominant observed relaxation mechanism is a harmonic mode at the plasma edge or reconnection near the CHI electrodes. In the case of an effective interelectrode distance approximately equal to the device minor radius, the ratio of toroidal plasma current to CHI injector current is maximized. Global magnetic equilibrium quantities and local magnetic measurements are consistent with modelling these open-flux discharges as thin current sheets connected to the CHI electrodes.
Air-stable n-channel organic thin-film transistors with high field-effect mobility based on N,N′-bis(heptafluorobutyl)-3,4:9,10-perylene diimide
Authors: Oh Joon Hak , Liu Shuhong , Bao Zhenan , Schmidt Rüdiger , Würthner Frank
Published: November 2007

The thin-film transistor characteristics of n-channel organic semiconductor, N,N′-bis(2,2,3,3,4,4,4-heptafluorobutyl)-perylene tetracarboxylic diimide, are described. The slip-stacked face-to-face molecular packing allows a very dense parallel arrangement of the molecules, leading to field-effect mobility as high as 0.72cm2V−1s−1. The mobility only slightly decreased after exposure to air and remained stable for more than 50days. Our results reveal that molecular packing effects such as close stacking of perylene diimide units and segregation effects imparted by the fluorinated side chains are crucial for the air stability.
Nanostructured barium titanate composites for embedded radio frequency applications
Authors: Biswas A. , Bayer I. S. , Karulkar P. C. , Tripathi A. , Avasthi D. K. , Norton M. G. , Szczech J. B.
Published: November 2007

We describe a vapor-phase codeposition method to fabricate a ceramic-in-polymer composite system comprising ferroelectric barium titanate nanoparticles in a highly polarizable polyaniline-polyurethane copolymer host. As-deposited composites exhibited a capacitance density of 15nF∕cm2 and a resonance frequency close to 100MHz with a loss tangent of 0.8. Annealing nanocomposites at 135°C resulted in slightly reduced but frequency-independent capacitance density (∼10nF∕cm2) with a loss tangent of 0.1 and resonance frequency at 200MHz. The interplay of polarization modes is discussed in relation to capacitor performance. The fabricated capacitors have potential for applications in embedded technology in the radio frequency.
Nonequilibrium transport of charge carriers and transient electroluminescence in organic light-emitting diodes
Authors: Nikitenko V. R. , von Seggern H.
Published: November 2007

An analytic theory of nonequilibrium hopping charge transport in disordered organic materials includes quasiequilibrium (normal) and extremely nonequilibrium (dispersive) regimes as limiting cases at long and short times, respectively. In the intermediate interval of time quasiequilibrium value of mobility is nearly established while the coefficient of field-assisted diffusion continues to increase (quasidispersive regime). Therefore, normalized time dependencies of transient current in time-of-flight (TOF) conditions are practically independent of field strength and sample thickness, in good agreement both with data of TOF experiments for molecularly doped polymers and results of numerical simulations of Gaussian disorder model. An analytic model of transient electroluminescence (TEL) is developed on the base of the mentioned theory. Strong asymmetry of mobilities is presumed. In analogy with TOF transients, dispersion parameter of normalized TEL intensity is anomalously large and almost field independent in the quasidispersive regime of transport. The method for determination of mobility from TEL data is proposed.
Stability analysis of internal ideal modes in low-shear tokamaks
Authors: Wahlberg C. , Graves J. P.
Published: November 2007

The stability of internal, ideal modes in tokamaks with low magnetic shear in the plasma core is analyzed. For equilibria with large aspect ratio, a parabolic pressure profile and a flat q profile in the core, an exact solution of the ideal magnetohydrodynamic (MHD) stability equations is found. The solution includes the eigenfunctions and the complete spectra of two distinctly different MHD phenomena: A family of fast-growing, Mercier-unstable global eigenmodes localized in a low-shear region with q<1, and another, related family of stable, global eigenmodes existing in plasmas with q>1 in the core. In the latter case the solution in addition includes one unstable eigenmode, if beta is larger than a critical value depending on the width of the low-shear region and on the q-profile in the edge region.
Four-point bisensitivity velocity interferometer with a multireflection etalon
Authors: Peng Qixian , Ma Ruchao , Li Zeren , Liu Jun , Chen Guanghua
Published: November 2007

A four-point bisensitivity velocity interferometer system for any reflector (VISAR) with a renovative delay etalon is proposed and demonstrated. In this interferometer, we introduce a new film-coating strategy to accurately measure small velocity with relatively short and cheap etalon. Laser pointing to the etalon is split into two beams with different incident angles with each beam going through the etalon in different path. The beam with the smaller incident angle is reflected three times before it leaves the etalon, while the other beam with larger incident angle goes through the etalon to and forth only once. The delay time of the laser beam with smaller incident angle is almost three times longer than that of the beam with larger incident angle. In the example of the laser with a smaller incident angle, the velocity per fringe of this interferometer can be reduced by approximately three times. The etalon is optimized so that four laser beams can be penetrated in the vertical direction at the meantime. With an etalon of 200mm in diameter and 150mm in length, a four-point bisensitivity velocity interferometer can achieve the velocity per fringe of 100 and 350m∕sfringe. A measurement has been successfully undertaken for the steel flyer driven by the explosive where the developed interferometer applies.
Structural and magnetic properties of nanocrystalline RuCo alloys
Authors: Qadri S. B. , Keller T. M. , Laskoski M. , Little C. A. , Osofsky M. S. , Khan H. R.
Published: November 2007

Nanoparticles of Ru1−xCox (0⩽x⩽1) in the carbon matrix were synthesized over the entire compositional range using organometallic precursors. For Co concentrations with x⩽0.75, a hexagonal close packed phase was formed, whereas a face centered cubic phase was observed for x>0.75. The crystallite sizes varied between 5 and 10nm. In addition, multiwalled carbon nanotubes formed during the pyrolysis of the precursors. Increasing ferromagnetic order was observed with increasing Co concentration.
High-intensity Brillouin light scattering by spin waves in a permalloy film under microwave resonance pumping
Authors: Stashkevich A. A. , Djemia P. , Fetisov Y. K. , Bizière N. , Fermon C.
Published: November 2007

A microwave assisted Brillouin light scattering (BLS) technique based on resonant excitation of spin waves in a 200 nm thick permalloy film by a micrometric size coplanar antenna has been studied. It has been demonstrated that the BLS intensity and signal-to-noise ratio have been improved by three orders of magnitude with respect to the conventional light scattering by thermal magnons. The analysis of the amplitude, shape, and frequency position of Stokes and anti-Stokes lines in the BLS spectra, for nonzero angles of the light incidence, indicates the presence of a strong hybridization of standing spin-wave resonances with propagating spin waves due to partial nonsymmetric pinning on the film surfaces. Direct optical probing has shown that the excited hybrid spin-wave modes are localized strictly in the vicinity of the microwave antenna.
Current-driven hydrogen incorporation in zinc oxide
Authors: Oh Min-Suk , Hwang Dae-Kue , Lim Jae-Hong , Choi Yong-Seok , Park Seong-Ju
Published: November 2007

The effect of electrical current on the hydrogen incorporation into single crystalline ZnO was investigated. The current-voltage characteristics of single crystalline ZnO were measured as a function of the electrical conductivity of ZnO. The electrical current of ZnO was significantly increased at the second sweep of voltages when the electrical conductivity of ZnO was higher than 0.32S∕cm. A depth profiling analysis of ZnO by dynamic secondary ion mass spectrometry indicated that the hydrogen atoms were incorporated to form hydrogen-related donors, such as a substitutional hydrogen (HO) and an interstitial hydrogen (Hi), which resulted in an increase in the donor concentration of ZnO.
Generation capacity adequacy evaluation based on peak load consideration
Authors: Saket R K , Bansal R C , Singh G
Published: November 2007

This paper describes a new methodology based on peak load consideration for reliability evaluation of a generation system. The methodology has been developed using Simpson?s (1/3)rd rule for loss of load probability (LOLP) evaluation. Load models are considered as straight line and stepped load duration curve for reliability evaluation. The LOLP evaluation is based on peak load consideration. The probability of load exceeding the generating capacity has also been considered in LOLP evaluation.
Tumor immune escape by the loss of homeostatic chemokine expression
Authors: Pivarcsi Andor , Müller Anja , Hippe Andreas , Rieker Juliane , van Lierop Anke , Steinhoff Martin , Seeliger Stephan , Kubitza Robert , Pippirs Ulrich , Meller Stephan , Gerber Peter A. , Liersch Ruediger , Buenemann Erich , Sonkoly Eniko , Wiesner Ulrike , Hoffmann Thomas K. , Schneider Leonid , Piekorz Roland , Enderlein Elaine , Reifenberger Julia , Rohr Ulrich-Peter , Haas Rainer , Boukamp Petra , Haase Ingo , Nürnberg Bernd , Ruzicka Thomas , Zlotnik Albert , Homey Bernhard
Published: November 2007

The novel keratinocyte-specific chemokine CCL27 plays a critical role in the organization of skin-associated immune responses by regulating T cell homing under homeostatic and inflammatory conditions. Here we demonstrate that human keratinocyte-derived skin tumors may evade T cell-mediated antitumor immune responses by down-regulating the expression of CCL27 through the activation of epidermal growth factor receptor (EGFR)–Ras–MAPK-signaling pathways. Compared with healthy skin, CCL27 mRNA and protein expression was progressively lost in transformed keratinocytes of actinic keratoses and basal and squamous cell carcinomas.In vivo, precancerous skin lesions as well as cutaneous carcinomas showed significantly elevated levels of phosphorylated ERK compared with normal skin, suggesting the activation of EGFR–Ras signaling pathways in keratinocyte-derived malignancies.In vitro, exogenous stimulation of the EGFR–Ras signaling pathway through EGF or transfection of the dominant-active form of the Ras oncogene (H-RasV12) suppressed whereas an EGFR tyrosine kinase inhibitor increased CCL27 mRNA and protein production in keratinocytes. In mice, neutralization of CCL27 led to decreased leukocyte recruitment to cutaneous tumor sites and significantly enhanced primary tumor growth. Collectively, our data identify a mechanism of skin tumors to evade host antitumor immune responses.
Increased ATPase activity produced by mutations at arginine-1380 in nucleotide-binding domain 2 of
ABCC8
causes neonatal diabetes
Authors: de Wet Heidi , Rees Mathew G. , Shimomura Kenju , Aittoniemi Jussi , Patch Ann-Marie , Flanagan Sarah E. , Ellard Sian , Hattersley Andrew T. , Sansom Mark S. P. , Ashcroft Frances M.
Published: November 2007

Gain-of-function mutations in the genes encoding the ATP-sensitive potassium (K
ATP
) channel subunits Kir6.2 (
KCNJ11
) and SUR1 (
ABCC8
) are a common cause of neonatal diabetes mellitus. Here we investigate the molecular mechanism by which two heterozygous mutations in the second nucleotide-binding domain (NBD2) of SUR1 (R1380L and R1380C) separately cause neonatal diabetes. SUR1 is a channel regulator that modulates the gating of the pore formed by Kir6.2. K
ATP
channel activity is inhibited by ATP binding to Kir6.2 but is stimulated by MgADP binding, or by MgATP binding and hydrolysis, at the NBDs of SUR1. Functional analysis of purified NBD2 showed that each mutation enhances MgATP hydrolysis by purified isolated fusion proteins of maltose-binding protein and NBD2. Inhibition of ATP hydrolysis by MgADP was unaffected by mutation of R1380, but inhibition by beryllium fluoride (which traps the ATPase cycle in the prehydrolytic state) was reduced. MgADP-dependent activation of K
ATP
channel activity was unaffected. These data suggest that the R1380L and R1380C mutations enhance the off-rate of P
i
, thereby enhancing the hydrolytic rate. Molecular modeling studies supported this idea. Because mutant channels were inhibited less strongly by MgATP, this would increase K
ATP
currents in pancreatic beta cells, thus reducing insulin secretion and producing diabetes.
The plant homeodomain finger of RAG2 recognizes histone H3 methylated at both lysine-4 and arginine-2
Authors: Ramón-Maiques Santiago , Kuo Alex J. , Carney Dylan , Matthews Adam G. W. , Oettinger Marjorie A. , Gozani Or , Yang Wei
Published: November 2007

Recombination activating gene (RAG) 1 and RAG2 together catalyze V(D)J gene rearrangement in lymphocytes as the first step in the assembly and maturation of antigen receptors. RAG2 contains a plant homeodomain (PHD) near its C terminus (RAG2-PHD) that recognizes histone H3 methylated at lysine 4 (H3K4me) and influences V(D)J recombination. We report here crystal structures of RAG2-PHD alone and complexed with five modified H3 peptides. Two aspects of RAG2-PHD are unique. First, in the absence of the modified peptide, a peptide N-terminal to RAG2-PHD occupies the substrate-binding site, which may reflect an autoregulatory mechanism. Second, in contrast to other H3K4me3-binding PHD domains, RAG2-PHD substitutes a carboxylate that interacts with arginine 2 (R2) with a Tyr, resulting in binding to H3K4me3 that is enhanced rather than inhibited by dimethylation of R2. Five residues involved in histone H3 recognition were found mutated in severe combined immunodeficiency (SCID) patients. Disruption of the RAG2-PHD structure appears to lead to the absence of T and B lymphocytes, whereas failure to bind H3K4me3 is linked to Omenn Syndrome. This work provides a molecular basis for chromatin-dependent gene recombination and presents a single protein domain that simultaneously recognizes two distinct histone modifications, revealing added complexity in the read-out of combinatorial histone modifications.
A role for DNA-mediated charge transport in regulating p53: Oxidation of the DNA-bound protein from a distance
Authors: Augustyn Katherine E. , Merino Edward J. , Barton Jacqueline K.
Published: November 2007

Charge transport (CT) through the DNA base pairs provides a means to promote redox reactions at a remote site and potentially to effect signaling between molecules bound to DNA. Here we describe the oxidation of a cell-cycle regulatory protein, p53, from a distance through DNA-mediated CT. A consensus p53 binding site as well as three DNA promoters regulated by p53 were synthesized containing a tethered DNA photooxidant, anthraquinone. Photoinduced oxidation of the protein occurs from a distance; introduction of an intervening CA mismatch, which inhibits DNA-mediated CT, prevents oxidation of p53. DNA-mediated oxidation is shown to promote dissociation of p53 from only some promoters, and this sequence-selectivity in oxidative dissociation correlates with the biological regulation of p53. Under severe oxidative stress, effected here through oxidation at long range, p53 dissociates from a promoter that activates DNA repair as well as the promoter for the negative regulator of p53, Mdm2, but not from a promoter activating cell-cycle arrest. Mass spectrometry results are consistent with disulfide bond formation in p53 upon DNA-mediated oxidation. Furthermore, DNA-bound p53 oxidation is shown
in vivo
by up-regulation of p53 and subsequent irradiation in the presence of a rhodium photooxidant to give a new p53 adduct that can be reversed with thiol treatment. This DNA-mediated oxidation of p53 parallels that seen by treating cells with hydrogen peroxide. These results indicate a unique mechanism using DNA-mediated CT chemistry by which p53 activity on different promoters may be controlled globally under conditions of oxidative stress.