bluuebunny/crossref_metadata_2025 huggingface dataset:
Short‐duration accelerated breathing challenges affect phonation
Authors: Sivasankar Mahalakshmi , Erickson Elizabeth
Published: June 2009

Objectives/Hypothesis:

Inhaled air must be adequately humidified to prevent vocal fold drying, which is detrimental to phonation. The water content of inspired air is reduced by parameters, such as increased breathing rate and oral route. Accelerated oral breathing challenges induce airway dehydration and are posited to affect airway function. The primary objective of this study was to investigate whether accelerated oral breathing challenges are detrimental to phonation. The secondary objective of this study was to determine whether individuals at increased risk for developing voice problems (i.e., smokers) have greater adverse phonatory effects after accelerated breathing challenge than nonsmoking controls.

Study Design:

Prospective study with between‐subjects, repeated‐measures design.

Methods:

Female smokers (n = 12) and nonsmoking controls (n = 12) participated in this experimental study over 2 days that differed in ambient humidity. Phonation threshold pressures (PTP) were collected prior to and following short‐term accelerated and habitual breathing challenges. Respiratory measures were collected during the challenges.

Results:

Short‐term accelerated breathing challenges significantly increased PTP. This increase in PTP with accelerated breathing was transient and not significantly influenced by breathing route, ambient humidity, or smoking status. Likewise, respiratory measures were not affected by breathing route, ambient humidity, or smoking status.

Conclusions:

During daily activities, such as exercise, individuals may engage in accelerated breathing for prolonged durations. This study demonstrates that even extremely short durations of accelerated breathing may affect phonation.
Using cells devoid of RAS proteins as tools for drug discovery
Authors: Urosevic Jelena , Sum Eleanor Y.M. , Moneo Victoria , Drosten Matthias , Dhawahir Alma , Becerra Mercedes , Carnero Amancio , Barbacid Mariano
Published: June 2009

Mutational activation of RAS proteins occurs in nearly 30% of all human tumors. To date direct pharmacological inhibition of RAS oncoproteins has not been possible. As a consequence, current strategies are focusing on the development of inhibitors that target those kinases acting downstream of RAS proteins, including those of the RAF/MEK/ERK and PI3K/AKT pathways. Most of these inhibitors have undesired off‐target effects that mask the potential therapeutic effect of blocking their targeted kinases. To facilitate the screening of selective inhibitors, we have generated lines of mouse embryonic fibroblasts that lack endogenous Ras proteins. These cells proliferate due to ectopic expression of either Ras oncoproteins that selectively activate the Raf/Mek/Erk pathway such as H‐RasG12V/D38E or constitutively active kinases such as B‐Raf and Mek1. These cell lines were exposed to inhibitors against the RAF, MEK, and AKT kinases as well as inhibitors of other kinases known to crosstalk with RAS signaling such as JNK and p38. Amongst all compounds tested, only the MEK inhibitors U0126 and PD0325901, showed the expected specificity pattern. Yet, PD0325901, but not U0126, was able to inhibit a cell line lacking Ras proteins that owed its proliferative properties to loss of p53. Thus, suggesting unexpected off‐target activities for this compound. The use of cell lines whose proliferative properties exclusively depend on selective targets provide a novel strategy to analyze the specificity of selective inhibitors designed against molecular targets implicated in human cancer. © 2009 Wiley‐Liss, Inc.
Multinuclear magnetic resonance studies of fluoronitroanilines
Authors: Gierczyk Błażej , Nowak‐Wydra Barbara , Mielcarek Aleksandra , Zalas Maciej , Grajewski Jakub
Published: June 2009

Ten fluoronitroanilines have been synthesized and the 1H, 13C, 15N and, 19F NMR spectra of these compounds have been recorded and fully assigned. Density functional theory(DFT) calculations have been performed for all compounds studied. Experimental and theoretical results are compared and the structure and atom character influence on the accuracy of the calculation discussed. Copyright © 2009 John Wiley & Sons, Ltd.
Accuracy and precision of MR blood oximetry based on the long paramagnetic cylinder approximation of large vessels
Authors: Langham Michael C. , Magland Jeremy F. , Epstein Charles L. , Floyd Thomas F. , Wehrli Felix W.
Published: June 2009

An accurate noninvasive method to measure the hemoglobin oxygen saturation (%HbO2) of deep‐lying vessels without catheterization would have many clinical applications. Quantitative MRI may be the only imaging modality that can address this difficult and important problem. MR susceptometry–based oximetry for measuring blood oxygen saturation in large vessels models the vessel as a long paramagnetic cylinder immersed in an external field. The intravascular magnetic susceptibility relative to surrounding muscle tissue is a function of oxygenated hemoglobin (HbO2) and can be quantified with a field‐mapping pulse sequence. In this work, the method's accuracy and precision was investigated theoretically on the basis of an analytical expression for the arbitrarily oriented cylinder, as well as experimentally in phantoms and in vivo in the femoral artery and vein at 3T field strength. Errors resulting from vessel tilt, noncircularity of vessel cross‐section, and induced magnetic field gradients were evaluated and methods for correction were designed and implemented. Hemoglobin saturation was measured at successive vessel segments, differing in geometry, such as eccentricity and vessel tilt, but constant blood oxygen saturation levels, as a means to evaluate measurement consistency. The average standard error and coefficient of variation of measurements in phantoms were <2% with tilt correction alone, in agreement with theory, suggesting that high accuracy and reproducibility can be achieved while ignoring noncircularity for tilt angles up to about 30°. In vivo, repeated measurements of %HbO2 in the femoral vessels yielded a coefficient of variation of less than 5%. In conclusion, the data suggest that %HbO2 can be measured reproducibly in vivo in large vessels of the peripheral circulation on the basis of the paramagnetic cylinder approximation of the incremental field. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Profile order and time‐dependent artifacts in contrast‐enhanced coronary MR angiography at 3T: Origin and prevention
Authors: Kotys Melanie S. , Herzka Daniel A. , Vonken Evert‐Jan , Ohayon Jacques , Heroux Julie , Gharib Ahmed M. , Stuber Matthias , Pettigrew Roderic I.
Published: June 2009

To enhance the clinical value of coronary magnetic resonance angiography (MRA), high‐relaxivity contrast agents have recently been used at 3T. Here we examine a uniform bilateral shadowing artifact observed along the coronary arteries in MRA images collected using such a contrast agent. Simulations were performed to characterize this artifact, including its origin, to determine how best to mitigate this effect, and to optimize a data acquisition/injection scheme. An intraluminal contrast agent concentration model was used to simulate various acquisition strategies with two profile orders for a slow‐infusion of a high‐relaxivity contrast agent. Filtering effects from temporally variable weighting in k‐space are prominent when a centric, radial (CR) profile order is applied during contrast infusion, resulting in decreased signal enhancement and underestimation of vessel width, while both pre‐ and postinfusion steady‐state acquisitions result in overestimation of the vessel width. Acquisition during the brief postinfusion steady‐state produces the greatest signal enhancement and minimizes k‐space filtering artifacts. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
In vivo measurement of ethanol metabolism in the rat liver using magnetic resonance spectroscopy of hyperpolarized [1‐13C]pyruvate
Authors: Spielman Daniel M. , Mayer Dirk , Yen Yi‐Fen , Tropp James , Hurd Ralph E. , Pfefferbaum Adolf
Published: June 2009

[1‐13C]Pyruvate is a readily polarizable substrate that has been the subject of numerous magnetic resonance spectroscopy (MRS) studies of in vivo metabolism. In this work 13C‐MRS of hyperpolarized [1‐13C]pyruvate was used to interrogate a metabolic pathway involved in neither aerobic nor anaerobic metabolism. In particular, ethanol consumption leads to altered liver metabolism, which when excessive is associated with adverse medical conditions including fatty liver disease, hepatitis, cirrhosis, and cancer. Here we present a method for noninvasively monitoring this important process in vivo. Following the bolus injection of hyperpolarized [1‐13C]pyruvate, we demonstrate a significantly increased rat liver lactate production rate with the coadministration of ethanol (P = 0.0016 unpaired t‐test). The affect is attributable to increased liver nicotinamide adenine dinucleotide (NADH) associated with ethanol metabolism in combination with NADH's role as a coenzyme in pyruvate‐to‐lactate conversion. Beyond studies of liver metabolism, this novel in vivo assay of changes in NADH levels makes hyperpolarized [1‐13C]pyruvate a potentially viable substrate for studying the multiple in vivo metabolic pathways that use NADH (or NAD+) as a coenzyme, thus broadening the range of applications that have been discussed in the literature to date. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Fast functional brain imaging using constrained reconstruction based on regularization using arbitrary projections
Authors: Grotz Thimo , Zahneisen Benjamin , Ella Arsène , Zaitsev Maxim , Hennig Jürgen
Published: June 2009

This work describes a novel method for highly undersampled projection imaging using constrained reconstruction by Tikhonov‐Phillips regularization and its application for high temporal resolution functional MRI (fMRI) at a repetition time of 80 ms. The high‐resolution reference image used as in vivo coil sensitivity is acquired in a separate acquisition using otherwise identical parameters. Activation studies using a standard checkerboard activation paradigm demonstrate the inherent high sensitivity afforded by the possibility to separate activation‐related effects from “physiological noise.”. In this first proof‐of‐principle of the constrained reconstruction based on regularization using arbitrary projections (COBRA) technique, experiments are performed in a single‐slice mode, which allows for a comparison with fast single‐slice echo‐planar imaging (EPI) at equal temporal resolution. The COBRA method can be extended to three‐dimensional (3D) encoding without severe penalty in temporal performance. Analysis of the global signal change demonstrates the excellent reproducibility of COBRA compared to standard EPI. Activation analysis is considerably improved by the possibility to remove electrocardiogram (ECG)‐related and breathing‐related signal fluctuations by physiological correction of each individual breathing and ECG cycle, respectively. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Mouse lumbar and cervical spinal cord blood flow measurements by arterial spin labeling: Sensitivity optimization and first application
Authors: Duhamel Guillaume , Callot Virginie , Decherchi Patrick , Le Fur Yann , Marqueste Tanguy , Cozzone Patrick J. , Kober Frank
Published: June 2009

In spinal cord injuries (SCI), tissue edema and consequent ischemia play an important role in neuronal damage. The assessment of quantitative spinal cord blood flow (SCBF) would be very valuable to help in understanding SCI pathophysiology. SCBF has previously been measured in animals with invasive techniques such as hydrogen clearance or labeled microspheres. A recent preliminary study also demonstrated the feasibility of assessing cervical SCBF by MRI with arterial spin labeling (ASL). However, due to bulk motion and field inhomogeneities, the feasibility of perfusion MRI at lower levels of the SC (thoracic, lumbar) remained an open question. In the present study, absolute SCBF measurements were carried out at both the cervical C3 and lumbar L1 levels of mouse SC using an adapted presaturated flow‐sensitive alternating inversion recovery (presat‐FAIR) ASL technique at 11.75T. Quantitative SCBF maps (resolution of 133 × 133 μm2) showed significantly lower gray matter (GM) perfusion values at the L1 level as compared to the C3 level (6% and 11% for the ventral and dorsal horns and 8% for total GM). The presat‐FAIR technique was then successfully applied to a mouse model of hemisection performed at the L1 level, illustrating the potential of ASL to help in SC pathology characterization. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Robust correction of spike noise: Application to diffusion tensor imaging
Authors: Chavez S. , Storey P. , Graham S.J.
Published: June 2009

Echo‐planar imaging (EPI) ‐based diffusion tensor imaging (DTI) is particularly prone to spike noise. However, existing spike noise correction methods are impractical for corrupted DTI data because the methods correct the complex MRI signal, which is not usually stored on clinical MRI systems. The present work describes a novel Outlier Detection De‐spiking technique (ODD) that consists of three steps: detection, localization, and correction. Using automated outlier detection schemes, ODD exploits the data redundancy available in DTI data sets that are acquired with a minimum of six different diffusion‐weighted images (DWIs) with similar signal and noise properties. A mathematical formulation, describing the effects of spike noise on magnitude images, yields appropriate measures for an outlier detection scheme used for spike detection while a normalization‐dependent outlier detection scheme is used for spike localization. ODD performs accurately on diverse DTI data sets corrupted by spike noise and can be used for automated control of DTI data quality. ODD can also be extended to other MRI applications with data redundancy, such as dynamic imaging and functional MRI. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Diffusion tensor imaging (DTI) of the brain in moving subjects: Application to in‐utero fetal and ex‐utero studies
Authors: Jiang Shuzhou , Xue Hui , Counsell Serena , Anjari Mustafa , Allsop Joanna , Rutherford Mary , Rueckert Daniel , Hajnal Joseph V.
Published: June 2009

We present a methodology to achieve 3D high‐resolution diffusion tensor image reconstruction of the brain in moving subjects. The source data is diffusion‐sensitized single‐shot echo‐planar images. After continuous scanning to acquire a repeated series of parallel slices with 15 diffusion directions, image registration is used to realign the images to correct for subject motion. Once aligned, the diffusion images are treated as irregularly‐sampled data where each voxel is associated with an appropriately rotated diffusion direction. This data is used to estimate the diffusion tensor on a regular grid. The method has been tested on data acquired at 1.5T from adults who deliberately moved and from eight fetuses imaged in utero. Maps of apparent diffusion coefficient (ADC) were reliably produced in all cases and promising performance was achieved for fractional anisotropy maps. Results from normal fetal brains were found to be consistent with published data from premature infants of similar gestational age. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Myocardial T mapping free of distortion using susceptibility‐weighted fast spin‐echo imaging: A feasibility study at 1.5 T and 3.0 T
Authors: Heinrichs Uwe , Utting Jane F. , Frauenrath Tobias , Hezel Fabian , Krombach Gabriele A. , Hodenius Michael A.J. , Kozerke Sebastian , Niendorf Thoralf
Published: June 2009

This study demonstrates the feasibility of applying free‐breathing, cardiac‐gated, susceptibility‐weighted fast spin‐echo imaging together with black blood preparation and navigator‐gated respiratory motion compensation for anatomically accurate T mapping of the heart. First, T maps are presented for oil phantoms without and with respiratory motion emulation (T = (22.1 ± 1.7) ms at 1.5 T and T = (22.65 ± 0.89) ms at 3.0 T). T relaxometry of a ferrofluid revealed relaxivities of R = (477.9 ± 17) mM−1s−1 and R = (449.6 ± 13) mM−1s−1 for UFLARE and multiecho gradient‐echo imaging at 1.5 T. For inferoseptal myocardial regions mean T values of 29.9 ± 6.6 ms (1.5 T) and 22.3 ± 4.8 ms (3.0 T) were estimated. For posterior myocardial areas close to the vena cava T‐values of 24.0 ± 6.4 ms (1.5 T) and 15.4 ± 1.8 ms (3.0 T) were observed. The merits and limitations of the proposed approach are discussed and its implications for cardiac and vascular T‐mapping are considered. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
A respiratory self‐gating technique with 3D‐translation compensation for free‐breathing whole‐heart coronary MRA
Authors: Lai Peng , Bi Xiaoming , Jerecic Renate , Li Debiao
Published: June 2009

Respiratory motion remains a major challenge for robust coronary MR angiography (MRA). Diaphragmatic navigator (NAV) suffers from indirect measurement of heart position. Respiratory self‐gating (RSG) approaches improve motion detection only in the head–feet direction, leaving motion in the other two dimensions unaccounted for. The purpose of this study was to extend conventional RSG (1D RSG) to RSG capable of 3D motion detection (3D RSG) by acquiring additional RSG projections with transverse‐motion‐encoding gradients. Simulation and volunteer studies were conducted to validate the effectiveness of this new method. Preliminary comparison was performed between coronary artery images reconstructed from the same datasets using different motion correction methods. Our simulation illustrates that a proper motion‐encoding gradient and derivation method enable accurate 3D motion detection. Results from whole‐heart coronary MRA show that 3D RSG can further reduce motion artifacts as compared to NAV and 1D RSG and enables use of larger gating windows for faster coronary imaging. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Quantitative spectroscopic imaging with in situ measurements of tissue water T1, T2, and density
Authors: Gasparovic C. , Neeb H. , Feis D.L. , Damaraju E. , Chen H. , Doty M.J. , South D.M. , Mullins P.G. , Bockholt H.J. , Shah N.J.
Published: June 2009

The use of tissue water as a concentration standard in proton magnetic resonance spectroscopy (1H‐MRS) of the brain requires that the water proton signal be adjusted for relaxation and partial volume effects. While single voxel 1H‐MRS studies have often included measurements of water proton T1, T2, and density based on additional 1H‐MRS acquisitions (e.g., at multiple echo or repetition times), this approach is not practical for 1H‐MRS imaging (1H‐MRSI). In this report we demonstrate a method for using in situ measurements of water T1, T2, and density to calculate metabolite concentrations from 1H‐MRSI data. The relaxation and density data are coregistered with the 1H‐MRSI data and provide detailed information on the water signal appropriate to the individual subject and tissue region. We present data from both healthy subjects and a subject with brain lesions, underscoring the importance of water parameter measurements on a subject‐by‐subject and voxel‐by‐voxel basis. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
In vivo lactate signal enhancement using binomial spectral‐selective pulses in selective MQ coherence (SS‐SelMQC) spectroscopy
Authors: Thakur S.B. , Yaligar J. , Koutcher J.A.
Published: June 2009

Tumor vasculature and tissue oxygen pressure can influence tumor growth, metastases, and patient survival. Elevated levels of lactate may be observed during the process of aggressive tumor development accompanied by angiogenesis (the evolution of the microenvironment). The noninvasive MR detection of lactate in tumor tissues as a potential biomarker is difficult due to the presence of co‐resonating lipids that are present at high concentrations. Methods were previously reported for lactate editing using the SELective Multiple Quantum Coherence (SelMQC) method. Here we report a sequence “SS‐SelMQC,” Spectral‐Selective SelMQC, which is a modified version of SelMQC using binomial pulses. Binomial pulses were employed in this editing sequence for frequency excitation or inversion of selective lactate resonances. Lactate detection has been demonstrated using SS‐SelMQC, both in vitro (30 mM lactate/H2O doped with 25 μM Gd‐DTPA) and in vivo (Dunning R3337‐AT prostate tumors), and compared to similar measurements made with SelMQC. Lactate areas were measured from nonlocalized spectra, one‐dimensional (1D) localized spectra, and two‐dimensional chemical shift images (CSI) of the localized slice. In data from whole phantoms, the modified pulse sequence yielded enhancement of the lactate signal of 2.4 ± 0.40 times compared to SelMQC. Similar in vivo lactate signal enhancement of 2.3 ± 0.24 times was observed in 1D slice‐localized experiment. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Manganese‐guided cellular MRI of human embryonic stem cell and human bone marrow stromal cell viability
Authors: Yamada Mayumi , Gurney Paul T. , Chung Jaehoon , Kundu Pratima , Drukker Micha , Smith Alan K. , Weissman Irving L. , Nishimura Dwight , Robbins Robert C. , Yang Phillip C.
Published: June 2009

This study investigated the ability of MnCl2 as a cellular MRI contrast agent to determine the in vitro viability of human embryonic stem cells (hESC) and human bone marrow stromal cells (hBMSC). Basic MRI parameters including T1 and T2 values of MnCl2‐labeled hESC and hBMSC were measured and viability signal of manganese (Mn2+)‐labeled cells was validated. Furthermore, the biological activity of Ca2+‐channels was modulated utilizing both Ca2+‐channel agonist and antagonist to evaluate concomitant signal changes. Metabolic effects of MnCl2‐labeling were also assessed using assays for cell viability, proliferation, and apoptosis. Finally, in vivo Mn2+‐guided MRI of the transplanted hESC was successfully achieved and validated by bioluminescence imaging. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Prospective head‐movement correction for high‐resolution MRI using an in‐bore optical tracking system
Authors: Qin Lei , van Gelderen Peter , Derbyshire John Andrew , Jin Fenghua , Lee Jongho , de Zwart Jacco A. , Tao Yang , Duyn Jeff H.
Published: June 2009

In MRI of the human brain, subject motion is a major cause of magnetic resonance image quality degradation. To compensate for the effects of head motion during data acquisition, an in‐bore optical motion tracking system is proposed. The system comprises two MR‐compatible infrared cameras that are fixed on a holder right above and in front of the head coil. The resulting close proximity of the cameras to the object allows precise tracking of its movement. During image acquisition, the MRI scanner uses this tracking information to prospectively compensate for head motion by adjusting the gradient field direction and radio frequency (RF) phases and frequencies. Experiments performed on subjects demonstrate robust system performance with translation and rotation accuracies of 0.1 mm and 0.15°, respectively. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
A new investigation of the extended Krylov subspace method for matrix function evaluations
Authors: Knizhnerman L. , Simoncini V.
Published: June 2009

For large square matrices A and functions f, the numerical approximation of the action of f(A) to a vector v has received considerable attention in the last two decades. In this paper we investigate theextended Krylov subspace method, a technique that was recently proposed to approximate f(A)v for A symmetric. We provide a new theoretical analysis of the method, which improves the original result for A symmetric, and gives a new estimate for A nonsymmetric. Numerical experiments confirm that the new error estimates correctly capture the linear asymptotic convergence rate of the approximation. By using recent algorithmic improvements, we also show that the method is computationally competitive with respect to other enhancement techniques. Copyright © 2009 John Wiley & Sons, Ltd.
Topology optimization of muffler internal partitions for improving acoustical attenuation performance
Authors: Lee Jin Woo , Kim Yoon Young
Published: June 2009

The internal partition configuration of an expansion chamber muffler affects significantly its acoustical transmission characteristics, but the use of systematic optimization methods to muffler design problems is rare. The main objective of this research is to maximize the transmission loss at target frequencies by optimizing partition layouts inside a muffler chamber by formulating an acoustical topology optimization problem. The selected target frequencies include the deep frequencies of a nominal muffler in order to see the critical effects of partition configurations on the acoustical transmission characteristics. The effects of partition volume constraint ratios are also investigated and physics behind the optimized layouts is investigated. Numerical results show that mufflers with optimized partition layouts outperform nominal mufflers considerably, but the shapes and locations of the optimized partitions should be much different from those of conventional partitions. Copyright © 2009 John Wiley & Sons, Ltd.
Analysis and implementation issues for the numerical approximation of parabolic equations with random coefficients
Authors: Nobile F. , Tempone Raul
Published: June 2009

We consider the problem of numerically approximating statistical moments of the solution of a time‐dependent linear parabolic partial differential equation (PDE), whose coefficients and/or forcing terms are spatially correlated random fields. The stochastic coefficients of the PDE are approximated by truncated Karhunen–Loève expansions driven by a finite number of uncorrelated random variables. After approximating the stochastic coefficients, the original stochastic PDE turns into a new deterministic parametric PDE of the same type, the dimension of the parameter set being equal to the number of random variables introduced.

After proving that the solution of the parametric PDE problem is analytic with respect to the parameters, we consider global polynomial approximations based on tensor product, total degree or sparse polynomial spaces and constructed by either a Stochastic Galerkin or a Stochastic Collocation approach. We derive convergence rates for the different cases and present numerical results that show how these approaches are a valid alternative to the more traditional Monte Carlo Method for this class of problems. Copyright © 2009 John Wiley & Sons, Ltd.
Using data in legacy fundraising: a practical approach
Authors: Magson Nigel , Routley Claire
Published: June 2009

Legacies provide a major source of income to charities, and their importance is only likely to increase with the passing on of the baby‐boomer generation. Legacy fundraising is a long‐term process, based on developing relationships with donors over time. Data have a key role to play in the development of these relationships, allowing legacy fundraisers to measure and track their donors, and to contribute to the development of effective fundraising strategies. This paper discusses the effective collection and use of data in legacy fundraising, from consolidating data, to analysing the results and building legacy targeting models. The authors discuss how these principles have been applied in UK‐based charity, Help the Aged, in conjunction with their Data Agency, Tangible Data (formerly Talking Numbers) and to give practical advice on how they may be implemented in other organisations.

Copyright © 2009 John Wiley & Sons, Ltd.
Time‐optimal control of automobile test drives with gear shifts
Authors: Kirches Christian , Sager Sebastian , Bock Hans Georg , Schlöder Johannes P.
Published: June 2009

We present a numerical method and results for a recently published benchmark problem (Optim. Contr. Appl. Met. 2005; 26:1–18; Optim. Contr. Appl. Met. 2006; 27(3):169–182) in mixed‐integer optimal control. The problem has its origin in automobile test‐driving and involves discrete controls for the choice of gears. Our approach is based on a convexification and relaxation of the integer controls constraint. Using the direct multiple shooting method we solve the reformulated benchmark problem for two cases: (a) As proposed in (Optim. Contr. Appl. Met. 2005; 26:1–18), for a fixed, equidistant control discretization grid and (b) As formulated in (Optim. Contr. Appl. Met. 2006; 27(3):169–182), taking into account free switching times. For the first case, we reproduce the results obtained in (Optim. Contr. Appl. Met. 2005; 26:1–18) with a speed‐up of several orders of magnitude compared with the Branch&Bound approach applied there (taking into account precision and the different computing environments). For the second case we optimize the switching times and propose to use an initialization based on the solution of (a). Compared with (Optim. Contr. Appl. Met. 2006; 27(3):169–182) we were able to reduce the overall computing time considerably, applying our algorithm. We give theoretical evidence on why our convex reformulation is highly beneficial in the case of time‐optimal mixed‐integer control problems as the chosen benchmark problem basically is (neglecting a small regularization term). Copyright © 2009 John Wiley & Sons, Ltd.
Preparation of albumin—PAA nanocapsules and their controlled release behavior for drugs
Authors: Wang Rong‐Min , Li Gang , Zhang Hui‐Fang , He Yu‐Feng , He Nai‐Pu , Lei Ziqiang
Published: June 2009

New kinds of narrowly distributed protein‐based nanoparticles, bovine serum albumin‐Poly (acrylic acid) (BSA/PAA) nanospheres, and nanocapsules were prepared via in situ polymerization, swelling, and re‐aggregation. The structure and morphology of the nanospheres were characterized by UV‐Vis, FT‐IR, DLS, and TEM. The stability of the BSA/PAA nanospheres and nanocapsules was increased when their skeletons were fixed by cross‐linked agents. The nanospheres carried a positive charge and their size was about 80–110 nm. The protein‐based nanocapsules were stimuli‐responsive with pH value and their hydrodynamic diameter varied from 70 to 230 nm with changes of pH. In vitro release experiments of Rhodamine B and Doxorubicin hydrochloride showed that these biopolymer nanoparticles provided a controlled release of the entrapped drugs for 300 hr. Copyright © 2009 John Wiley & Sons, Ltd.
Silver sulfide as a staining agent for scanning electron microscopy of nylon 6/MXD6 blends
Authors: Magniez Kevin , Fox Bronwyn L , Looney Mark G
Published: June 2009

BACKGROUND: In transmission and scanning electron microscopy imaging, the ability to obtain sufficient contrast between the components of a blend when they are both of a similar chemical structure still remains problematic. This paper investigates the domain morphology of a polymer blend containing two polyamides, nylon 6 and the semi‐aromatic polyamide poly(m‐xylene adipamide) (MXD6), using scanning electron microscopy in backscattered electron imaging mode. The efficiency of three staining agents, ruthenium tetroxide, phosphotungstic acid and silver sulfide, in obtaining optimum phase contrast between the two polymers is discussed.

RESULTS: The use of silver sulfide as a staining agent was found to be a fast and reliable approach which required basic sample preparation and provided excellent compositional contrast between the phases present in the nylon 6/MXD6 blends compared to the other staining agents.

CONCLUSIONS: The technique described in this paper is believed to be a novel and versatile method that has the potential to further improve the ability to study complex polymer blends where one polymer contains an aromatic ring. Copyright © 2009 Society of Chemical Industry
Synthesis of Cibacron Blue F3GA‐coupled magnetic PMMA nanospheres and their use for protein affinity separation
Authors: Qu Feng , Guan Yueping , Ma Zhiya , Zhang Qiang
Published: June 2009

BACKGROUND: New magnetic carrier separation technologies, capable of treating dilute solutions in large‐scale processes, even in the presence of biological debris, are necessary for the future development of biotechnology. Non‐porous magnetic carriers are more resistant to fouling, show better mass transfer and have lower non‐specific adsorption than porous carriers. Nanosized magnetic carriers have a surface area comparable to that of typical macroporous resins, and therefore their application has advantages.

RESULTS: Magnetic poly(methyl methacrylate) (PMMA) nanospheres with an average diameter of 76 nm and narrow size distribution were prepared by a facile mini‐emulsion polymerization. After surface modification with poly(ethylene glycol), Cibacron Blue F3GA (CB) was coupled to the magnetic PMMA nanospheres to form dye ligand‐attached magnetic adsorbents for bovine serum albumin (BSA) adsorption. The CB‐coupled magnetic PMMA nanospheres showed very high adsorption capacity (121.98 mg g−1) and little non‐specific adsorption for BSA. The adsorbed protein could be easily desorbed using high ionic strength solution.

CONCLUSION: The CB‐coupled magnetic PMMA nanospheres showed a high BSA adsorption capacity, low non‐specific adsorption and fast adsorption kinetics in comparison with other dye‐affinity adsorbents. These characteristics indicate that these magnetic PMMA nanospheres have great potential for protein affinity separation and purification. Copyright © 2009 Society of Chemical Industry
Anomalous rheological behavior of poly(1‐vinyl‐2‐pyrrolidone) and CuCl2 in solution and their interactions in solid composites
Authors: Hao Chaowei , Zhao Ying , Dong Xia , Zhou Yong , Xu Yizhuang , Wang Dujin , Lai Guoqiao , Jiang Jianxiong
Published: June 2009

BACKGROUND: The aggregation structure of polymers in solution is an important aspect of their behavior. The interactions between metal ions and water‐soluble polymers have a significant influence on the conformation behavior of biological macromolecules, and on the ionic selectivity of cells, etc.

RESULTS: The rheological behavior of poly(1‐vinyl‐2‐pyrrolidone) (PVP) and CuCl2 dispersed in N,N‐dimethylformamide was investigated using rheological techniques. Concentrated solutions containing CuCl2 exhibited a rheological behavior different from those containing other metal chlorides (LiCl, CaCl2 and CoCl2). This indicated that the variation in the aggregation state of the PVP chains with concentration of CuCl2 was different from those of PVP solutions containing Li+, Ca2+ or Co2+ ions.

CONCLUSION: The interactions between PVP and CuCl2 inhibit the crystallization of CuCl2 and induce the formation of microphase separation in the system. Copyright © 2009 Society of Chemical Industry
Synthesis of poly(fluorinated styrene)‐block‐poly(ethylene oxide) amphiphilic copolymers via atom transfer radical polymerization: potential application as paper coating materials
Authors: Ibrahim Khalid A , Al‐Muhtaseb Ala'a H , Seppälä Jukka
Published: June 2009

BACKGROUND: The surface of a substrate which comprises a fibrous material is brought into contact with a type of amphiphilic block copolymer which comprises hydrophilic/hydrophobic polymeric blocks. These amphiphilic copolymers have been synthesized by atom transfer radical polymerization (ATRP) technique. The atom transfer radical polymerization of poly(2,3,4,5,6‐pentafluorostyrene)‐block‐poly(ethylene oxide) (PFS‐b‐PEO) copolymers (di‐ and triblock structures) with various ranges of PEO molecular weights was initiated by a PEO chloro‐telechelic macroinitiator. The polymerization, carried out in bulk and catalysed by copper(I) chloride in the presence of 2,2′‐bipyridine ligand, led to A–B–A amphiphilic triblock and A–B amphiphilic diblock structures.

RESULTS: With most of the macroinitiators, the living nature of the polymerizations led to block copolymers with narrow molecular weight distributions (1.09 < Mw/Mn < 1.33) and well‐controlled molecular structures. These block copolymers turned out to be water‐soluble through adjustment of the PEO block content (>90 wt%). Of all the block copolymers synthesized, PFS‐b‐PEO(10k)‐b‐PFS containing 10 wt% PFS was found to retard water absorption considerably.

CONCLUSION: The printability of paper treated with the copolymers was evaluated with contact angle measurements and felt pen tests. The adsorption of such copolymers at the solid/liquid interface is relevant to the wetting and spreading of liquids on hydrophobic/hydrophilic surfaces. Copyright © 2009 Society of Chemical Industry
Synthesis and characterization of a series of diverse poly(2‐oxazoline)s
Authors: Kempe Kristian , Lobert Matthias , Hoogenboom Richard , Schubert Ulrich S.
Published: June 2009

This article describes the synthesis and characterization of a variety of new poly(2‐oxazoline)s. With regard to functional polymers, 2‐oxazolines represent an interesting class of monomers because of the easy variation of the substituent in 2‐position. Starting from the corresponding nitriles, different 2‐oxazolines were obtained containing a diverse set of 2‐substituents, including thioether bonds (M11), trifluoromethyl groups (M8, M10), and alkyl‐ or aryl groups (M1–M7). The subsequent polymerization of the majority of these monomers proceeded in a living manner, which was demonstrated by linear first‐order kinetics, a linear increase of molar mass with conversion, and relatively narrow molar mass distributions. In addition, selected thermal and surface properties of the polymers were studied utilizing DSC and contact‐angle measurements to determine the effects of different 2‐substituents on the macroscopic properties. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3829–3838, 2009
Synthesis and characterization of hyperbranched polyesters from glycerol‐based AB2 monomer
Authors: Parzuchowski Pawel G. , Grabowska Martyna , Jaroch Michal , Kusznerczuk Monika
Published: June 2009

This article describes the synthesis of a new glycerol‐based AB2 type monomer—ethyl{3‐[2‐hydroxy‐1‐(hydroxymethyl)ethoxy]propyl}thioacetate (4) and its application for the preparation of hyperbranched polyesters. The polycondensation of 4 has been performed over a wide range of catalysts and reaction conditions leading to polymers containing solely primary hydroxyl groups. The polycondensation progress has been monitored by means of 1H NMR. The degree of branching of the polymers showed to be in the range of 0.5 ± 0.03. The obtained polyesters easily undergo hydrolysis or alcoholysis and may be of interest as recycled materials. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3860–3868, 2009
Synthesis and properties of nitrogen‐linked poly(2,7‐carbazole)s as hole‐transport material for organic light emitting diodes
Authors: Michinobu Tsuyoshi , Kumazawa Hiroe , Otsuki Eiji , Usui Hiroaki , Shigehara Kiyotaka
Published: June 2009

A novel class of carbazole polymers, nitrogen‐linked poly(2,7‐carbazole)s, was synthesized by polycondensation between two bifunctional monomers using the palladium‐catalyzed amination reaction. The polymers were characterized by 1H NMR, Infrared, Gel permeation chromatography, and MALDI‐TOF MS and it was revealed that the combination of the monomer structures is important for producing high molecular weight polymers. Thermal analysis indicated a good thermal stability with high glass transition temperatures, e.g., 138 °C for the higher molecular weight polymer P2. To pursue the application possibilities of these polymers, their optical properties and energy levels were investigated by UV‐Vis absorption and fluorescence spectra as well as their electrochemical characteristics. Although the blue light emission was indeed observed for all polymers in solution, the quantum yields were very low and the solid films were not fluorescent. On the other hand, the HOMO levels of the polymers estimated from the onset potentials for the first oxidation in the solid thin films were relatively high in the range of −5.12 to −5.20 eV. Therefore, light emitting diodes employing these polymers as a hole‐transport layer and iridium(III) complex as a triplet emitter were fabricated. The device of the nitrogen‐linked poly(2,7‐carbazole) P3 with p,p′‐biphenyl spacer, which has a higher HOMO level and a higher molecular weight, showed a much better performance than the device of P2 with m‐phenylene spacer. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3880–3891, 2009
General description of the structure of branched polymers
Authors: Gray‐Weale Angus , Gilbert Robert G.
Published: June 2009

A multidimensional distribution function is defined to describe the branching structure of branched homopolymers such as starch and polyacrylates. Averages of this function give distributions which can be measured using, for example, the number and weight distributions as a function of hydrodynamic volume from size‐exclusion chromatography and field‐flow fractionation, and two‐dimensional separation methods. This provides means to plot data to obtain physically meaningful quantities, and to test mechanistic postulates for the (bio)synthesis, of branched polymers. A simple enzyme‐kinetic model for a reduced form of this multidimensional distribution for starch biosynthesis is derived and solved. One application is to derive number distributions for the molecular weight distribution of debranched glycogen. Fitting this to experiment gives estimates of this ratio for two forms of glycogen. We propose that number distributions from size separation for starch (which, it is pointed out, are obtained directly from in‐line viscometric detection) have a simple and meaningful form when plotted as ln(number distribution) against Vhp, where Vh is hydrodynamic volume, and p a parameter of order unity determined from multiple‐detection size separation measurements. The new function is also used to propose a two‐dimensional experiment which can yield an unambiguous measurement of the amylose: amylopectin ratio in starch. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3914–3930, 2009
Thermal curing behavior of MWCNT modified vinyl ester‐polyester resin suspensions prepared with 3‐roll milling technique
Authors: Seyhan A. T. , de la Vega Alejandra , Tanoglu M. , Schulte K.
Published: June 2009

This study aims to investigate the curing behavior of a vinyl ester‐polyester resin suspensions containing 0.3 wt % of multiwalled carbon nanotubes with and without amine functional groups (MWCNTs and MWCNT‐NH2). For this purpose, various analytical techniques, including Differential Scanning Calorimetry (DSC), Fourier infrared spectroscopy (FTIR), Raman Spectroscopy, and Thermo Gravimetric Analyzer (TGA) were conducted. The resin suspensions with carbon nanotubes (CNTs) were prepared via 3‐roll milling technique. DSC measurements showed that resin suspensions containing CNTs exhibited higher heat of cure (Q), besides lower activation energy (Ea) when compared with neat resin. For the sake of simplicity of interpretation, FTIR investigations were performed on neat vinyl ester resin suspensions containing the same amount of CNTs as resin. As a result, the individual fractional conversion rates of styrene and vinyl ester were interestingly found to be altered dependent on MWCNTs and MWCNT‐NH2. The findings obtained from RS measurements of the cured samples are highly proportional to those obtained from FTIR measurements. TGA measurements revealed that CNT modified nanocomposites have higher activation energy of degradation (Ed) compared with the cured polymer. The findings obtained revealed that CNTs with and without amine functional groups alter overall thermal curing response of the surrounding matrix resin, which may probably impart distinctive characteristics to mechanical behavior of the corresponding nanocomposites achieved. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1511–1522, 2009
Deamidation of α‐synuclein
Authors: Robinson Noah E. , Robinson Matthew L. , Schulze Stephanie E. S. , Lai Bert T. , Gray Harry B.
Published: June 2009

The rates of deamidation of α‐synuclein and single Asn residues in 13 Asn‐sequence mutants have been measured for 5 × 10−5M protein in both the absence and presence of 10−2M sodium dodecyl sulfate (SDS). In the course of these experiments, 370 quantitative protein deamidation measurements were performed and 37 deamidation rates were determined by ion cyclotron resonance Fourier transform mass spectrometry, using an improved whole protein isotopic envelope method and a mass defect method with both enzymatic and collision‐induced fragmentation. The measured deamidation index of α‐synuclein was found to be 0.23 for an overall deamidation half‐time of 23 days, without or with SDS micelles, owing primarily to the deamidation of Asn(103) and Asn(122). Deamidation rates of 15 Asn residues in the wild‐type and mutant proteins were found to be primary sequence controlled without SDS. However, the presence of SDS micelles slowed the deamidation rates of nine N‐terminal region Asn residues, caused by the known three‐dimensional structures induced through protein binding to SDS micelles.
Structure and stability of icosahedral particles of a covalent coat protein dimer of bacteriophage MS2
Authors: Plevka Pavel , Tars Kaspars , Liljas Lars
Published: June 2009

Particles formed by the bacteriophage MS2 coat protein mutants with insertions in their surface loops induce a strong immune response against the inserted epitopes. The covalent dimers created by fusion of two copies of the coat protein gene are more tolerant to various insertions into the surface loops than the single subunits. We determined a 4.7‐Å resolution crystal structure of an icosahedral particle assembled from covalent dimers and compared its stability with wild‐type virions. The structure resembled the wild‐type virion except for the intersubunit linker regions. The covalent dimer orientation was random with respect to both icosahedral twofold and quasi‐twofold symmetry axes. A fraction of the particles was unstable in phosphate buffer because of assembly defects. Our results provide a structural background for design of modified covalent coat protein dimer subunits for use in immunization.
Two alternative modes for optimizing nylon‐6 byproduct hydrolytic activity from a carboxylesterase with a β‐lactamase fold: X‐ray crystallographic analysis of directly evolved 6‐aminohexanoate‐dimer hydrolase
Authors: Ohki Taku , Shibata Naoki , Higuchi Yoshiki , Kawashima Yasuyuki , Takeo Masahiro , Kato Dai‐ichiro , Negoro Seiji
Published: June 2009

Promiscuous 6‐aminohexanoate‐linear dimer (Ald)‐hydrolytic activity originally obtained in a carboxylesterase with a β‐lactamase fold was enhanced about 80‐fold by directed evolution using error‐prone PCR and DNA shuffling. Kinetic studies of the mutant enzyme (Hyb‐S4M94) demonstrated that the enzyme had acquired an increased affinity (Km = 15 mM) and turnover (kcat = 3.1 s−1) for Ald, and that a catalytic center suitable for nylon‐6 byproduct hydrolysis had been generated. Construction of various mutant enzymes revealed that the enhanced activity in the newly evolved enzyme is due to the substitutions R187S/F264C/D370Y. Crystal structures of Hyb‐S4M94 with bound substrate suggested that catalytic function for Ald was improved by hydrogen‐bonding/hydrophobic interactions between the AldCOOH and Tyr370, a hydrogen‐bonding network from Ser187 to AldNH, and interaction between AldNH and Gln27‐Oε derived from another subunit in the homo‐dimeric structure. In wild‐type Ald‐hydrolase (NylB), Ald‐hydrolytic activity is thought to be optimized by the substitutions G181D/H266N, which improve an electrostatic interaction with AldNH (Kawashima et al., FEBS J 2009; 276:2547–2556). We propose here that there exist at least two alternative modes for optimizing the Ald‐hydrolytic activity of a carboxylesterase with a β‐lactamase fold.