bluuebunny/crossref_metadata_2025_split huggingface dataset:
Competitive Equilibria in Atom Transfer Radical Polymerization
Authors: Tsarevsky Nicolay V. , Braunecker Wade A. , Vacca Alberto , Gans Peter , Matyjaszewski Krzysztof 
Published: March 2007

AbstractWith the recent development of new initiation techniques in atom transfer radical polymerization (ATRP) that allow catalysts to be employed at unprecedented low concentrations (∼10 ppm), a thorough understanding of competitive equilibria that can affect catalyst performance is becoming increasingly important. Such mechanistic considerations are discussed herein, including i) factors affecting the position of the ATRP equilibrium; ii) dissociation of the ATRP catalyst at high dilution and loss of deactivator due to halide dissociation; iii) conditional stability constants as related to competitive monomer, solvent, and reducing agent complexation as well as ligand selection with respect to protonation in acidic media; and iv) competitive equilibria involving electron transfer reactions, including the radical oxidation to carbocations or reduction to carbanions, radical coordination to the metal catalyst, and disproportionation of the CuI‐based ATRP activator.
RAFT Polymerization in Bulk and Emulsion
Authors: Buttè Alessandro , Peklak A. David , Storti Giuseppe , Morbidelli Massimo 
Published: March 2007

AbstractDetailed models of the RAFT polymerization in both non‐segregated (bulk) and segregated (seeded emulsion) systems are presented. It is shown that satisfactory agreements between experiments and models can be achieved, and that effects such as inhibition and retardation, or the polymerization behavior at high conversions can be readily explained. In all cases the model parameter fitting has been minimized, being mostly limited to the rate coefficients of the addition/fragmentation reactions in the RAFT polymerization. Therefore, such models are believed to be invaluable tools towards a deeper understanding of the main phenomena underlying RAFT polymerization.
Size‐Exclusion Effect and Protein Repellency of Concentrated Polymer Brushes Prepared by Surface‐Initiated Living Radical Polymerization
Authors: Yoshikawa Chiaki , Goto Atsushi , Ishizuka Norio , Nakanishi Kazuki , Kishida Akio , Tsujii Yoshinobu , Fukuda Takeshi 
Published: March 2007

AbstractThe adsorption of proteins on poly(2‐hydroxyethyl methacrylate) (PHEMA) brushes was systematically investigated from the viewpoint of the size‐exclusion effect of the concentrated brushes. By use of surface‐initiated atom transfer radical polymerization, well‐defined, concentrated PHEMA brushes were successfully grafted on the inner surface of the silica monolithic column with meso pores of ca. 80 nm as well as a silicon wafer and a quartz crystal microbalance (QCM) chip. By eluting low‐polydispersity pullulans with different molecular weight through the modified monolithic column, the concentrated PHEMA brush was characterized and demonstrated to sharply exclude solute molecules with the critical molecular size (size‐exclusion limit) comparable to the distance between the nearest‐neighboring graft points d. The elution behaviors of proteins with different sizes were studied with this PHEMA‐grafted column: the protein sufficiently larger than the critical size was perfectly excluded from the brush layer and separated only in the size‐exclusion mode by the meso pores without affinity interaction with the brush surface. Then, the irreversible adsorption of proteins on PHEMA brushes was investigated using QCM by varying graft densities (σ = 0.007, 0.06, and 0.7 chains/nm2) and protein sizes (effective diameter = 2–13 nm). A good correlation between the protein size and the graft density was observed: proteins larger than d caused no significant irreversible adsorption on the PHEMA brushes. Thus, we experimentally substantiated the postulated size‐exclusion effect of the concentrated brushes and confirmed that this effect plays an important role for suppressing protein adsorption.
Synthesis of Rod‐Coil Block Copolymers using Two Controlled Polymerization Techniques
Authors: Steig Simone , Cornelius Frauke , Heise Andreas , Knoop Rutger J. I. , Habraken Gijs J. M. , Koning Cor E. , Menzel Henning 
Published: March 2007

AbstractA double‐headed initiator was synthesized yielding two functional groups for the initiation of the nickel mediated ring‐opening polymerization of γ‐benzyl‐L‐glutamate‐N‐carboxyanhydride and controlled radical polymerization of vinyl monomers via ATRP or NMP. Well‐defined block copolymers combining polypeptides and synthetic polymers were obtained.
Unusual Kinetics in Aqueous Heterophase Polymerizations
Authors: Tauer Klaus , Mukhamedjanova Muyassar , Holtze Christian , Nazaran Pantea , Lee Jeongwoo 
Published: March 2007

AbstractThe heterogeneous nature of aqueous heterophase polymerizations is the base for an easy route to unique block copolymers, for the development of new and more effective polymerization strategies, and the abilities to unique studies of radical polymerization kinetics. Thermo‐sensitive double hydrophilic block copolymers and micro‐ or nano‐gel particles of poly(N‐isopropyl acrylamide) as thermo‐responsible block and charged or uncharged hydrophilic polymers can easily be prepared if the polymerization of N‐isopropyl acrylamide is started with the corresponding polymeric radicals. The application of extremely fast microwave heating allows the development of highly effective pulsed thermal polymerization strategies and the production of polymers with desired molecular weight distributions over wide ranges. 2,2′‐azobisisobutyronitrile simultaneously initiates the polymerization in both the monomer and the aqueous phase and leads, even under surfactant‐free conditions, to stable latex particles.
Surface – Functionalized Inorganic Nanoparticles in Miniemulsion Polymerization
Authors: Töpfer Oliver , Schmidt‐Naake Gudrun 
Published: March 2007

AbstractTwo inorganic cores, consisting of silica and titania, have been prepared via basic Stoeber synthesis. Those cores have been functionalized, using trimethoxysilyl propylmethacrylate (MPTMS) and introduced into a miniemulsion copolymerization system. The miniemulsion consisted of styrene (S) and 2‐hydroxyethyl methacrylate (HEMA), styrene sulfonic acid (SSA) or aminoethyl methacrylate hydrochloride (AEMA) as comonomer in varying compositions. The morphology of the products has been investigated by SEM and dynamic light scattering (DLS) measurements. The composition of the products has been investigated by photoacoustic FTIR (PA‐FTIR) spectroscopy and elemental analysis. Thermal properties have been determined by TGA and DSC analysis.
A Study of Microstructures and Properties of High‐Carbon Si‐Cr Cast Steel Containing Rare Earth and Titanium
Authors: Fu H. , Miao Y. , Chen X. , Hu K. , Tian Z. 
Published: March 2007

AbstractThe microstructure, tensile and impact behaviour of high‐carbon Si‐Cr cast steel containing rare earth (RE) and titanium have been determined after austempering. The additions of RE and titanium refined the primary austenite grain size resulting in improving toughness. The addition of silicon handicapped the formation of carbide and carbide‐free bainitic ferrite and carbon enriched retained austenite could be obtained in the austempering structures of high‐carbon Si‐Cr cast steel, which had excellent mechanical properties and abrasion resistance. Moreover, the basic tendency of the mechanical properties of high‐carbon Si‐Cr cast steel influenced by the austempering temperature was that the hardness and tensile strength reduced and the impact toughness and fracture toughness increased with increasing temperature. The comprehensive properties were the best while austempering at 330oC.
Development of Wear and Corrosion Resistant Metal Matrix Composites with hard Particles formed in Situ
Authors: Weber S. , Berns H. 
Published: March 2007

AbstractMetal matrix composites (MMC) were developed, consisting of hardenable steel matrices and embedded particles of titanium nitride (TiN) or vanadium nitride (VN) formed in situ during the consolidation by hot isostatic pressing (HIP). Designing wear and corrosion resistant materials was the objective of this development. The materials were produced by means of powder metallurgy and are composed of a ferrritic stainless steel powder X4CrMo15–1 and crushed particles of ferro titanium or ferro vanadium, respectively. These powder mixtures were first heat treated in an N2‐atmosphere for alloying with nitrogen and subsequently consolidated to wear resistant MMC by HIP. This publication describes the necessary processing steps, taking into account thermodynamic equilibrium calculations with Thermo‐Calc.
Eigenspannung im mit gasdruckunterstütztem Feingussverfahren hergestellten langfaserverstärkten Aluminium‐Matrix‐Verbundwerkstoff
Authors: Sun S. , Rosefort M. , Bäumer A. , Chauhan D. , Possel‐Dölken I. , Bührig‐Polaczek A. 
Published: March 2007

AbstractDie Eigenspannungen zwischen Matrix und Faser in einer mit dem gasdruckunterstütztem Feingussverfahren hergestellten γ‐Al2O3‐langfaserverstärkten Aluminiumlegierung AlZn6Mg1Ag1 wurden mit der Röntgenbeugungsmethode experimentell gemessen und mit FEM numerisch simuliert. Die Ergebnisse haben wider Erwarten gezeigt, dass die durchschnittlichen Eigenspannungen sowohl in der Matrix als auch in der Faser nicht sehr groß sind. Allerdings sind die Eigenspannungen sehr ungleichmäßig verteilt. An der Grenzfläche in der Matrix gibt es in der Faserquer‐ und Faserlängsrichtung jeweils einen kleinen Bereich mit relativ hohen Zugeigenspannungen. Durch die Analyse der Eigenspannung in mit verschiedenen Faservolumenanteilen verstärkten Proben wurde der Einfluss des Faservolumenanteils im Verbundwerkstoff analysiert. Tendenziell steigt die Zugeigenspannung in der Matrix und sinkt die Druckeigenspannung in der Faser mit zunehmendem Faservolumenanteil. Wenn der Faservolumenanteil 65 % überschreitet, erreichen die endgültigen maximalen Zugeigenspannungen in der Matrix die Streckgrenze der Aluminiumlegierung und es entsteht lokale plastische Verformung in der Matrix.
Olfactory loss may be a first sign of idiopathic Parkinson's disease
Authors: Haehner Antje , Hummel Thomas , Hummel Cornelia , Sommer Ulrike , Junghanns Susann , Reichmann Heinz 
Published: March 2007

AbstractRecent studies support the idea of olfactory dysfunction as a very early sign of idiopathic Parkinson's disease (IPD). Aim of the present study was to clinically follow‐up patients with idiopathic hyposmia to find out the percentage of patients developing IPD after 4 years time. At baseline, olfactory tests had been combined with transcranial sonography of the substantia nigra and 123I‐FP‐CIT SPECT imaging. At the present neurological examination, 7% of the individuals with idiopathic hyposmia had developed clinical IPD. Altogether, 13% presented with abnormalities of the motor system. Our data suggest that a combination of olfactory testing and other tests may constitute a screening tool for the risk to develop IPD. © 2007 Movement Disorder Society
Levodopa response in Parkinsonism with multiple mitochondrial DNA deletions
Authors: Wilcox Robert A. , Churchyard Andrew , Dahl Henrik H. , Hutchison Wendy M. , Kirby Denise M. , Thyagarajan Dominic 
Published: March 2007

AbstractWe report a patient with an autosomal dominant chronic progressive external ophthalmoplegia phenotype associated with multiple mtDNA deletions in muscle from a family in which linkage analysis excluded mutations in DNA polymerase γ (POLG), adenine nucleotide translocase (ANT‐1) or C10orf2 (Twinkle). She presented with prominent Parkinsonism characterized by prolonged benefit from levodopa (L‐dopa) and the later development of L‐dopa induced dyskinesias and motor fluctuations. Thus L‐dopa responsiveness, L‐dopa induced dyskinesias and motor fluctuations may also occur in atypical Parkinsonism of mitochondrial disease, just as they may in multiple system atrophy. © 2007 Movement Disorder Society
Sweating in Parkinsonian patients with wearing‐off
Authors: Pursiainen Ville , Haapaniemi Tarja H. , Korpelainen Juha T. , Sotaniemi Kyösti A. , Myllylä Vilho V. 
Published: March 2007

AbstractDisorders of the autonomic nervous system are common in Parkinson's disease (PD). Earlier studies suggest that some nonmotor symptoms may fluctuate with the motor symptoms, but the possible interrelationship between motor phenomena and sweating has not been studied. The authors measured sweating by using an evaporimeter on three different areas of the body (right hand, left hand, chest) immediately before the morning PD medication (baseline), and thereafter hourly up to 4 hour, in 16 PD patients with wearing‐off type of motor fluctuations and in 15 patients without clinical motor fluctuations. The clinical state of the patients was evaluated using the Unified Parkinson's Disease Rating Scale motor score every hour. Sweating increased during the 4‐hour follow‐up, and reached its maximum level at the time of the highest Unified Parkinson's Disease Rating Scale motor score phase (off‐stage) in patients with wearing‐off (initially affected hand, P = 0.007; left hand, P = 0.004; right hand, P = 0.034), but in the patients without wearing‐off no changes in sweating were observed during the follow‐up. Sweating of the left hand (P < 0.001), right hand (P < 0.001), and initially affected hand (P = 0.008) during the whole observation period was significantly higher in patients with motor fluctuations than in those without. The present study shows that sweating fluctuates in conjunction with wearing‐off phenomenon. © 2007 Movement Disorder Society
Neurological deficits are associated with increased brain calcinosis, hypoperfusion, and hypometabolism in idiopathic basal ganglia calcification
Authors: Saiki Misuzu , Saiki Shinji , Sakai Koichiro , Matsunari Ichiro , Higashi Kotaro , Murata Ken‐ya , Hattori Nobutaka , Hirose Genjiro 
Published: March 2007

AbstractWe report two familial cases of idiopathic basal ganglia calcification. A 60‐year‐old proband with choreoathetosis, dysarthria, and cognitive decline showed more extensive brain calcinosis, hypoperfusion, and hypometabolism than did his asymptomatic 82‐year‐old mother. The mother had no frontal lobe calcinosis but basal ganglia and dentate nucleus depositions were detectable. Perfusion neuroimaging, however, was normal in the asymptomatic mother and abnormal in the clinically impaired proband. The presence of calcinosis cannot be used as an index of neurological impairment but the extent of calcinosis and reduction in perfusion and metabolism may be useful for separating symptomatic from asymptomatic subjects with IBGC. These findings suggest that an interruption of neuronal circuitry may cause neurological deficits. The degree of neurological deficits may correlate with the severity of calcinosis and the reduction of perfusion and metabolism. © 2007 Movement Disorder Society
Ciprofloxacin‐induced palatal tremor
Authors: Cheung Yuk‐Fai , Wong Winnie Wing‐Yin , Tang Kwok‐Wing , Chan John Hiu‐Ming , Li Patrick Chung‐Ki 
Published: March 2007

AbstractWe describe an 84‐year‐old man with an unusual clinical presentation of palatal tremor in association with ciprofloxacin treatment. The patient had rhythmical movements not only of the soft palate but also of the face and trunk. Complete resolution of the symptoms occurred 2 days after discontinuation of ciprofloxacin and administration of sodium valproate. This is the first reported case of palatal tremor secondary to the use of ciprofloxacin. © 2007 Movement Disorder Society
Detection of 13C‐labeled metabolites in the in vivo canine heart by B1 insensitive heteronuclear coherent polarization transfer and comparison of signal enhancement with NOE
Authors: Wei Haoran , Merkle Hellmut , Xu Ya , Ellermann Jutta , Sipprell Kevin , Uǧurbil Kǎmil 
Published: March 2007

AbstractA recently developed adiabatic coherent polarization transfer enhancement technique [H. Merkle, H. Wei, M. Garwood, K. Uǧurbil. J. Magn. Reson. 99, 480–494 (1992)] was employed to perform 13C spectroscopy in the intact canine heart in vivo during [2‐13C]‐acetate infusion into the left descending coronary artery; the results were compared with 13C spectra obtained with conventionally employed nuclear Overhauser enhancement. The results demonstrate that both methods can be performed by using surface coils to obtain in vivo 13C spectra and that coherent polarization transfer provides better enhancement than NOE for [2‐13C]‐acetate but not for short T2 compounds.
Multi‐gradient echo with susceptibility inhomogeneity compensation (MGESIC): Demonstration of fMRI in the olfactory cortex at 3.0 T
Authors: Yang Qing X. , Dardzinski Bernard J. , Li Shizhe , Eslinger Paul J. , Smith Michael B. 
Published: March 2007

AbstractShort image acquisition times and sensitivity to magnetic susceptibility favor the use of gradient echo imaging methods in functional MRI (fMRI). However, magnetic susceptibility effects attributed to air‐tissue interfaces also lead to severe signal loss in images of the large inferior frontal and lateral temporal cortices of the human brain, which renders these regions inaccessible to fMRI. The signal loss is caused by the local field gradients in the slice selection direction. A multigradient echo with magnetic susceptibility inhomogeneity compensation method (MGESIC) is proposed to overcome this problem. The MGESIC method effectively corrects the susceptibility artifacts and maintains the advantages of gradient echo methods to both BOLD sensitivity and fast image acquisition. The effectiveness of the MGESIC method is demonstrated by fMRI experimental results within the olfactory cortex.
Time‐resolved projection angiography after bolus injection of contrast agent
Authors: Hennig Jürgen , Scheffler Klaus , Laubenberger Jörg , Strecker Ralf 
Published: March 2007

AbstractA method for MR angiography after bolus injection of a normal dose (0.1 mmol/kg) of contrast agent is presented. Projection angiograms are acquired with a non‐slice selective Snapshot FLASH sequence with a time resolution of 1 s per image or better. Typically 40 to 60 images are acquired consecutively after bolus injection of a contrast agent. The signal from vessels can be separated from background by postprocessing based on the observed temporal evolution of the signal intensities during bolus passage. The subsecond projection MR‐DSA is a reliable and robust technique to produce high resolution anatomical images of the vascular system avoiding the necessity of exact timing of the contrast agent bolus. It also supplies functional information about the hemodynamics in the observed region including perfusion.
Effect of temperature in focal ischemia of rat brain studied by 31P and 1H spectroscopic imaging
Authors: Kozlowski Piotr , Buchan Alastair M. , Tuor Ursula I. , Xue Dong , Huang Zhi‐Gao , Chaundy Karen E. , Saunders John K. 
Published: March 2007

Abstract31P, 1H and lactate spectroscopic imaging was used to evaluate the effects of hypothermia on focal cerebral ischemia produced by middle cerebral artery occlusion. The effects on high energy phosphate metabolism, pH, lactate and NAA were investigated in 24 spontaneously hypertensive rats subjected to either permanent or transient ischemia. Under either normothermic (37.5°C) or hypothermic (32°C) conditions, with permanent 6‐h occlusion, there was little difference between groups in either the NMR measurements or the volume of infarction. In animals that underwent 3 h of ischemia followed by 12 h of reperfusion, the ischemic changes in lactate, pH, NAA, and high‐energy phosphate returned toward control values, and there was a protective effect of hypothermia (infarct volume of 211 ± 26 and 40 ± 14 mm3 in normothermic and hypothermic groups, respectively). Thus, hypothermia did not ameliorate the changes in lactate, pH, NAA, or high energy phosphate levels occurring during ischemia, however, during reperfusion there was an improvement in both the recovery of these metabolites and pathological outcome in hypothermic compared with normothermic animals.
13C editing of glutamate in human brain using J‐refocused coherence transfer spectroscopy at 4.1 T
Authors: Pan Jullie W. , Mason Graeme F. , Vaughan J. Thomas , Chu Wen‐Jang , Zhang Yantian , Hetherington Hoby P. 
Published: March 2007

AbstractThe method of single quantum 13C editing is analyzed and implemented with water suppressed J‐refocused coherence transfer spectroscopy. Analysis of the 13C inversion pulse demonstrates that it is optimally placed into the second echo of the J‐refocused sequence. We have used this method to acquire 13C‐edited spectra of glutamate from phantoms and in vivo. The turnover of 13C4‐labeled glutamate in human brain in vivo was observed in parasagittal gray matter using a volume head coil at 4.1 T with a time resolution of 5.3 min.
Temperature dependence and phase transition of proton relaxation of hydrated collagen in intact beef tendon specimens via cross‐relaxation spectroscopy
Authors: Tzou Der‐Lii , Lee Shu‐Ming , Yeung Hong N. 
Published: March 2007

AbstractThe role of water of hydration in proton relaxation in tissues as exemplified by hydrated collagen in beef tendon was studied as a function of temperature from −40° to 37°C by using cross‐relaxation spectroscopy. Experimental data were fitted to a simple binary spin‐bath model. The outcome of this procedure allows the construction of a semi‐quantitative depiction of proton relaxation in a heterogeneous system and its change as one of the water fractions freezes at about −10 to −20°C, a transition observed by NMR and confirmed independently by differential scanning calorimetry. Such physical depiction provides a crude but insightful interpretation of the role “bound” water plays in proton relaxation. This may be important in shedding light on the mechanism of tissue relaxation and its role in MRI diagnosis, particularly for those diseases such as liver cirrhosis where the water‐macromolecular interaction plays a prominent role.
Estimating NAA in cortical gray matter with applications for measuring changes due to aging
Authors: Lim Kelvin O. , Spielman Daniel M. 
Published: March 2007

AbstractN‐acetylaspartic acid (NAA), a prominent peak in the proton spectrum, is an amino acid thought to be present almost exclusively in neurons and their dendritic and axonal extensions. While 1H MRS studies are showing promise in identifying NAA deficits in different patient groups, unwanted lipid signal from subcutaneous fat surrounding the skull, and necessarily large voxels have limited investigators' ability to assess NAA in cortical gray matter. Here we report a technique developed to derive estimates of NAA signal from cortical gray matter. This approach uses an inversion recovery imaging pulse sequence with a long TE to suppress lipid signal from the scalp and information from concurrently obtained structural MR images to determine the CSF, white and gray matter composition of each spectroscopic voxel. A regression analysis is then used to estimate what NAA levels would be in “pure” white and gray matter voxels. This technique has been applied to demonstrate reduced NAA gray/white levels in the brains of five healthy older compared with five healthy younger women.