bluuebunny/crossref_metadata_2025 huggingface dataset:
Jenbach Tunnel – a shallow hydroshield drive
Authors: Gamper Christian , Knapp Michael , Fiest Thomas
Published: September 2009

The joint venture “Arge Tunnel Jenbach” consisting of the firms Strabag, Züblin and Hochtief was awarded the Jenbach Tunnel contract H8 in summer 2006. This contract section is part of the northern approach to the Brenner Base Tunnel and belongs to the trans‐European TEN1 axis Berlin‐Palermo. The main part of the contract is a 3,470 m long two‐track tunnel with an excavated diameter of 13 m and an excavated cross‐section of 133 m2, which was driven with a hydroshield. Tunnelling started in October 2007, with breakthrough in April 2009. The particular features of this tunnel are the very shallow overburden and the alignment.

Another part of the project was the construction of seven rescue shafts and their connection to the main tunnel. Six of these connecting tunnels pass through loose ground and groundwater and were constructed with a jacked pipe of external diameter 4.8 m. Also part of the project were a cut‐and‐cover tunnel with a length of 230 m, a ramp structure as groundwater trough with a length of 610 m and the construction of the link to the existing tracks with a length of 870 m.

Die Arbeitsgemeinschaft Arge Tunnel Jenbach bestehend aus den Firmen Strabag, Züblin und Hochtief hat im Sommer 2006 den Auftrag für das Baulos H8 Tunnel Jenbach erhalten. Dieses Baulos ist ein Teil der Zulaufstrecke Nord zum Brennerbasistunnel und gehört zur transeuropäischen TEN1 Achse Berlin‐Palermo. Der Hauptteil des Bauloses ist ein 3.470 m langer zweigleisiger Tunnel mit einem Durchmesser von 13 m und einem Ausbruchquerschnitt von 133 m2, der mit einem Hydroschild aufgefahren wurde. Vortriebsbeginn war im Oktober 2007, der Durchschlag erfolgte im April 2009. Die Besonderheiten des Tunnels waren seine oberflächennahe Trassierung und die Linienführung.

Weiterer Bestandteil des Bauvorhabens ist die Herstellung von sieben Rettungsschächten und deren Verbindung zum Haupttunnel. Sechs dieser Verbindungsstollen liegen im Lockermaterial und Grundwasser und wurden im Rohrvorpressverfahren mit einem Außendurchmesser von 4,8 m aufgefahren. Zusätzliche Bestandteile des Bauvorhabens sind ein Tunnel in offener Bauweise mit einer Länge von 230 m, ein Rampenbauwerk als Grundwasserwanne mit einer Länge von 610 m und die Herstellung der Verknüpfungsstelle mit den Bestandgleisen mit einer Länge von 870 m.
The management of excavated materials from the Lyon‐Turin rail link project
Authors: Burdin Jacques , Monin Nathalie
Published: September 2009

The Lyon‐Turin rail link project is a major part of the European Corridor no. 5, Lisbon‐Kiev. The management and use of the excavated materials have been identified as one of the major issues concerning project approval since the very first stage of the study. The following paper describes the methods chosen by the French and Italian authorities to improve the use of some 20 million t resulting from the excavation of 150 km of tunnels, representing 60 million t of materials. The presentation mainly focuses on two tunnels, the Chartreuse tunnel – 24.7 km, two tubes – and the base tunnel Maurienne‐Ambin – approx. 53 km, two tubes – under the Alps between France and Italy. All the tools today available are being used by the designer in order to prepare the tender documents, including industrial test production of concrete aggregates. The important role of the owner of the project is also mentioned with the aim of optimising the management and recycling of the excavated materials.

Das Eisenbahnprojekt Lyon‐Turin ist wesentlicher Teil des Transeuropäischen Korridors Nr. 5, Lissabon‐Kiew. Zu den größten Problemen hinsichtlich des Genehmigungsverfahrens wurden schon zu Beginn des Planungsprozesses die Bewirtschaftung und Wiederverwertung des Tunnelausbruchmaterials erkannt. Der vorliegende Beitrag beschreibt die Vorgehensweisen der französischen und italienischen Behörden zur Erhöhung des Anteils des wiederverwerteten Ausbruchmaterial aus insgesamt 150 km Tunnel auf 20 Mio t bei einer gesamten Ausbruchmenge von 60 Mio t. Die Präsentation konzentriert sich hierbei auf den 24, 7 km langen, zweiröhrigen Chartreuse‐Tunnel und den ungefähr 53 km langen, zweiröhrigen alpenquerenden Basistunnel Maurienne‐Ambin zwischen Frankreich und Italien. Zur Erstellung der Ausschreibungsunterlagen wurden seitens der Planer alle heutzutage zur Verfügung stehenden Mittel herangezogen, die auch eine großmaßstäbliche Testproduktion von Betonzuschlagstoffen beinhaltet. Dabei wird auch auf die bedeutende Rolle des Auftraggebers des Projekts bezüglich der Optimierung der Bewirtschaftung und Wiederverwendung des Ausbruchmaterials hingewiesen.
The convergence confinement method as an aid in the design of deep tunnels
Authors: Kainrath‐Reumayer Stefan , Gschwandtner Gunter , Galler Robert
Published: September 2009

The convergence confinement method is used in its original form for the analytic or graphical description of the ground and system behaviour of underground excavations. The purpose of the method is to derive the support measures required from the combination of the ground characteristic curve, a model of the development of the radial deformations of the excavation surface in the axial direction of the tunnel, the support characteristic curve and the installation time and location of the support measures. The convergence confinement method is mostly used in the preliminary design of underground structures.

Typical applications of the convergence confinement method are deep tunnels and tunnels with ground behaviour types where displacements play a major role. If sudden ruptures occur, in shallow tunnelling and in loose ground, this method is not to be recommended. An absolute precondition for the correct use is an understanding of the theory of the convergence confinement method and the course of failure mechanisms in the rock mass and their effects on the system behaviour.

Das Kennlinienverfahren (KLV) dient in seinen ursprünglichen Entstehungsformen zur analytischen oder grafischen Beschreibung des Gebirgs‐ und Systemverhaltens von untertägigen Hohlraumbauten. Ziel des Verfahrens ist es, aus der Kombination von der Gebirgskennlinie (GKL), einem Modell der Entwicklung der radialen Hohlraumrandverschiebungen in Tunnellängsrichtung, der Ausbaukennlinie und dem Einbauzeitpunkt sowie ‐ort der Stützmittel den notwendigen Stützmitteleinsatz abzuleiten. Das Kennlinienverfahren findet seinen Einsatz vorwiegend in der Vorbemessung von untertägigen Hohlraumbauten.

Typische Anwendungsbereiche des Kennlinienverfahrens sind tiefliegende Tunnel und Tunnel mit Gebirgsverhaltenstypen, bei denen Deformationen eine große Rolle spielen. Bei Auftreten abrupter Bruchvorgänge, im seichtliegenden Tunnelbau und im Lockergestein ist dieses Verfahren nicht empfehlenswert. Unabdingbare Voraussetzung für eine korrekte Anwendung sind das Verständnis der Theorie des Kennlinienverfahrens und der Abläufe der Bruchvorgänge im Gebirge und deren Auswirkung auf das Systemverhalten.
Complex grouting tasks at home and abroad as seen by the contractor
Authors: Breit Klaus
Published: September 2009

“The devil is in the detail” – this is particularly true for the implementation of complex grouting work. The term grouting includes a number of sophisticated processes including waterproofing, stabilisation, pressure tunnel, compensation, inclined shaft, vacuum, consolidation, sealing curtain, alluvial and rock grouting. The formulation of injection criteria, as part of the design as well as for construction, varies as much as the descriptions of these techniques. Some criteria are explained through examples from the point of view of the contractor.

“Die Tücke liegt im Detail” – ganz besonders gilt dies für die Durchführung komplexer Injektionsaufgaben. Unter dem Begriff Injektion verbergen sich zahlreiche anspruchsvolle Bauverfahren, unter anderen Abdicht‐, Verfestigungs‐, Druckstollen‐, Hebungs‐, Schrägschacht‐, Vakuum‐, Consolidation‐, Dichtschleier‐, Alluvial‐, und Felsinjektionen. So verschieden wie die Bezeichnungen sind die Anforderungen an die Formulierung von Injektionskriterien, sowohl in der Planung als auch in der Ausführung. Anhand von Beispielen werden einige Kriterien aus ausführungstechnischer Sicht erläutert.
DRG prospective payment systems: refine or not refine?
Authors: Hafsteinsdottir Elin Johanna Gudrun , Siciliani Luigi
Published: September 2009

We present a model of contracting between a purchaser of health services and a provider (a hospital). We assume that hospitals provide two alternative treatments for a given diagnosis: a less intensive one (for example, a medical treatment) and a more intensive one (a surgical treatment). We assume that prices are set equal to the average cost reported by the providers, as observed in many OECD countries (yardstick competition). The purchaser has two options: (1) to set one tariff based on the diagnosis only and (2) to differentiate the tariff between the surgical and the medical treatment (i.e. to refine the tariff). We show that when tariffs are refined, the provider has always an incentive to overprovide the surgical treatment. If the tariff is not refined, the hospital underprovides the surgical treatment (and overprovides the medical treatment) if the degree of altruism is sufficiently low compared with the opportunity cost of public funds. Our main result is that price refinement might not be optimal. Copyright © 2009 John Wiley & Sons, Ltd.
Prediction of hypocalcemia after using 1‐ to 6‐hour postoperative parathyroid hormone and calcium levels: An analysis of pooled individual patient data from 3 observational studies
Authors: Jumaily Jeffrey Saad , Noordzij J. Pieter , Dukas Alex G. , Lee Stephanie L. , Bernet Victor J. , Payne Richard J. , McLeod Ian K. , Hier Michael P. , Black Martin J. , Kerr Paul D. , Raffaelli Marco , Bellantone Rocco , Lombardi Celestino P. , Dietrich Mary S.
Published: September 2009

Background.

Parathyroid hormone (PTH) levels up to 6 hours postthyroidectomy have been shown to have excellent predictive power in determining hypocalcemia. In this study, we investigate the usefulness of combining calcium and PTH to increase the predictive power.

Methods.

Individual patient data were obtained from 3 studies (152 patients) that fulfilled our criteria (using PTH assay within hours postthyroidectomy to predict symptomatic hypocalcemia).

Results.

Changes in combined PTH and calcium threshold levels checked 1 to 6 hours after thyroidectomy were excellent in predicting postoperative hypocalcemia. A decrease in PTH of 60%, coupled with a simultaneous decrease in calcium of 10%, 5 to 6 hours postoperatively resulted in a sensitivity and specificity of 100%. However, combined PTH and calcium threshold changes were not significantly better than using PTH threshold changes alone.

Conclusions.

Threshold changes in serum calcium and PTH, checked hours after surgery, can be used together to accurately predict whether a patient will become hypocalcemic after thyroidectomy. © 2009 Wiley Periodicals, Inc. Head Neck, 2010
Candida famata modulates toll‐like receptor, β‐defensin, and proinflammatory cytokine expression by normal human epithelial cells
Authors: Bahri Raouf , Saidane‐Mosbahi Dalila , Rouabhia Mahmoud
Published: September 2009

Candida albicans is no longer the only yeast involved in infectious disorders, as others, such as C. famata, commonly associated with foods as well as terrestrial and marine environments, are being recognized as potential emerging pathogens that cause human candidiasis. We investigated the interaction between C. famata and human epithelial cells using monolayer cultures and an engineered human oral mucosa (EHOM). C. famata was able to adhere to gingival epithelial cells but failed to adopt the hyphal form in the presence/absence of proteins. Interestingly, when cultured onto the engineered human oral mucosa (EHOM), C. famata formed a biofilm and invaded the connective tissue. When normal human gingival epithelial cells were put in contact with C. famata, they expressed high levels of Toll‐like receptors (TLR)‐2, ‐4, and ‐6, but not TLR‐9 mARN. The upregulation of TLRs was paralleled by an increase of IL‐1β and TNFα, but not IFNγ mARN expression, suggesting the involvement of specific pro‐inflammatory cytokines (IL‐1β and TNFα) in the defense against infection with C. famata. The active role of epithelial cells in the innate immunity against C. famata infection was enhanced by their capacity to express high levels of human β‐defensin (HBD)‐1, ‐2, and ‐3. The upregulation of pro‐inflammatory cytokines and antimicrobial peptide expression may explain the growth inhibition of C. famata by the gingival epithelial cells. Overall results provide additional evidence of the involvement of C. famata in the activation of innate immunity and the contribution of human epithelial cells in local defenses against such exogenous stimulations as C. famata infections. J. Cell. Physiol. 222:209–218, 2010. © 2009 Wiley‐Liss, Inc.
Bone loss induced by Runx2 Over‐expression in mice is blunted by osteoblastic over‐expression of TIMP‐1
Authors: Schiltz Corinne , Prouillet Christophe , Marty Caroline , Merciris Didier , Collet Corinne , de Vernejoul Marie‐Christine , Geoffroy Valérie
Published: September 2009

The Runx2 gene is essential for osteoblast differentiation and function. In vivo over‐expression of Runx2 in osteoblasts increases bone resorption, and blocks terminal osteoblast differentiation. Several lines of evidence suggest that osteoblastic matrix metalloproteinases (MMPs) could contribute to the increased bone resorption observed in mice over‐expressing Runx2 (Runx2 mice). The goal of our study was to use a transgenic approach to find out whether the inhibition of osteoblastic MMPs can reduce the bone loss induced by the over‐expression of Runx2. We analyzed the effect of the in vivo over‐expression of the TIMP‐1 in osteoblasts on the severe osteopenic phenotype in Runx2 mice. Females with the different genotypes (WT, Runx2, TIMP‐1 and TIMP‐1/Runx2) were analyzed for bone density, architecture, osteoblastic and osteoclastic activity and gene expression using qPCR. TIMP‐1 over‐expression reduces the bone loss in adult Runx2 mice. The prevention of the bone loss in TIMP‐1/Runx2 mice was due to a combination of reduced bone resorption and sustained bone formation. We present evidence that the ability of osteoblastic cells to induce osteoclastic differentiation is lower in TIMP‐1/Runx2 mice than in Runx2 mice, probably due to a reduction in the expression of RANK‐L and of the Runx2 transgene. Osteoblast primary cells from TIMP‐1/Runx2 mice, but not from Runx2 mice, were able to differentiate into fully mature osteoblasts producing high osteocalcin levels. In conclusion, our findings suggest that osteoblastic MMPs can affect osteoblast differentiation. Our work also indicates that osteoblastic MMPs are partly responsible for the bone loss observed in Runx2 transgenic mice. J. Cell. Physiol. 222:219–229, 2010. © 2009 Wiley‐Liss, Inc.
Potential of 1H MR spectroscopic imaging to segregate patients who are likely to show malignancy of the peripheral zone of the prostate on biopsy
Authors: Kumar Virendra , Jagannathan Naranamangalam R. , Kumar Rajeev , Nayyar Rishi , Thulkar Sanjay , Gupta Siddhartha D. , Hemal Ashok K. , Gupta Narmada P.
Published: September 2009

Purpose

To evaluate the potential of MR spectroscopic imaging (MRSI) to segregate patients who, upon prostate biopsy, are more likely to show a malignancy in the peripheral zone (PZ) of the prostate gland.

Materials and Methods

Before biopsy, MRSI was carried in 123 men with elevated prostate specific antigen level or an abnormal digital rectal examination. After the MRSI investigation, all patients underwent systematic transrectal ultrasound guided biopsy and were categorized using standard random number tables into the following two groups: (i) Group I, a 62 member training set; and (ii) Group II, a 61‐member test set. The cutoff value for the [citrate/(choline+creatine)] ratio for patients in the training set was obtained using the receiver operating characteristic (ROC) curve method. This value was then applied to the test set of patients as well.

Results

The ROC method gave a cutoff value of 1.2 for the [Citrate/(Choline+Creatine)] ratio. When applied as a malignancy‐predictor to the test group of patients (Group II), the ROC method generated the following results: sensitivity, 77%; specificity, 83%; negative predictive value, 93%; positive predictive value, 55% and accuracy, 82%.

Conclusion

The results indicate that patients who are deemed as malignancy‐positive in the PZ by MRSI using the ROC cutoff may be subjected to prostate biopsy to confirm the diagnosis of cancer. J. Magn. Reson. Imaging 2009. © 2009 Wiley‐Liss, Inc.
Assessing fibre‐rich feedstuffs in pig nutrition: comparison of methods and their potential implications
Authors: Sappok Maria , Pellikaan Wilbert F , Verstegen Martin WA , Sundrum Albert
Published: September 2009

BACKGROUND: In organic farming, roughage has to be added to pigs' daily rations for animal welfare reasons. Since little is known about how roughage affects pigs, seven carbohydrate‐rich feedstuffs (corn silage, ryegrass, turnip leaf, turnip tuber, Jerusalem artichoke and two types of clover–ryegrass silage) were tested using two different in vitro methods—total tract digestibility and the gas production technique—to determine apparent digestibility by observing organic matter loss. The aim was to determine whether the results of different methods and treatments lead to similar results or rankings.

RESULTS: The in vitro enzymatic incubation method showed 3–20% lower fermentabilities than the in vitro fermentation process. The pretreatment of substrates with enzymes before fermentation led to similar fermentabilities but different gas production kinetics compared to the fermentation of untreated substrates. Using two different inocula generated no significant differences. When the feedstuffs were ranked by their fermentability, the rank order was relatively similar for both methods.

CONCLUSIONS: Different methods and pretreatments lead to different fermentabilities while a ranking of the results gives a similar order. Both methods seem to be appropriate tools for assessing feedstuffs. In order to determine which feedstuff is best utilised by the animal, further investigations of both digestibility and gas production kinetics are required. Copyright © 2009 Society of Chemical Industry
Staging laparoscopy enhances the detection of occult metastases in patients with pancreatic adenocarcinoma
Authors: Contreras Carlo M. , Stanelle Eric J. , Mansour John , Hinshaw J. Louis , Rikkers Layton F. , Rettammel Robert , Mahvi David M. , Cho Clifford S. , Weber Sharon M.
Published: September 2009

Background

The use of staging laparoscopy has been highly institutional dependent. We sought to assess the incidence of occult intra‐abdominal metastases identified at the time of staging laparoscopy for patients with either potentially resectable or locally advanced pancreatic adenocarcinoma (LAPC). We also compared the rate of occult metastases in patients who underwent staging laparoscopy versus laparotomy.

Methods

Patients were confirmed to have potentially resectable or LAPC at a multidisciplinary hepatopancreaticobiliary conference. Patients with potentially resectable lesions were initially explored via staging laparoscopy or laparotomy, based on surgeon preference.

Results

Over a 4‐year period, 25 patients with potentially resectable tumors and 33 patients with LAPC were staged with laparoscopy, with an equivalent prevalence of occult metastases found at laparoscopy (28% potentially resectable vs. 33% LAPC, P = 0.8). Fifty‐two patients with potentially resectable lesions were explored initially via laparotomy. Occult peritoneal metastases were more likely to be detected in patients with potentially resectable tumors that were explored via laparoscopy than via laparotomy (32% vs. 10%, P = 0.018).

Conclusions

Staging laparoscopy is more likely than open exploration to detect occult metastases. Current preoperative imaging inadequately identifies unresectable pancreatic adenocarcinoma; therefore, all patients with potentially resectable disease should undergo staging laparoscopy. J. Surg. Oncol. 2009;100:663–669. © 2009 Wiley‐Liss, Inc.
Magnetic resonance imaging of facial nerve schwannoma
Authors: Thompson Andrew L. , Aviv Richard I. , Chen Joseph M. , Nedzelski Julian M. , Yuen Heng‐Wai , Fox Allan J. , Bharatha Aditya , Bartlett Eric S. , Symons Sean P.
Published: September 2009

Objectives/Hypothesis:

This study characterizes the magnetic resonance (MR) appearances of facial nerve schwannoma (FNS). We hypothesize that the extent of FNS demonstrated on MR will be greater compared to prior computed tomography studies, that geniculate involvement will be most common, and that cerebellar pontine angle (CPA) and internal auditory canal (IAC) involvement will more frequently result in sensorineural hearing loss (SNHL).

Study Design:

Retrospective study.

Methods:

Clinical, pathologic, and enhanced MR imaging records of 30 patients with FNS were analyzed. Morphologic characteristics and extent of segmental facial nerve involvement were documented.

Results:

Median age at initial imaging was 51 years (range, 28–76 years). Pathologic confirmation was obtained in 14 patients (47%), and the diagnosis reached in the remainder by identification of a mass, thickening, and enhancement along the course of the facial nerve. All 30 lesions involved two or more contiguous segments of the facial nerve, with 28 (93%) involving three or more segments. The median segments involved per lesion was 4, mean of 3.83. Geniculate involvement was most common, in 29 patients (97%). CPA (P = .001) and IAC (P = .02) involvement was significantly related to SNHL. Seventeen patients (57%) presented with facial nerve dysfunction, manifesting in 12 patients as facial nerve weakness or paralysis, and/or in eight with involuntary movements of the facial musculature.

Conclusions:

This study highlights the morphologic heterogeneity and typical multisegment involvement of FNS. Enhanced MR is the imaging modality of choice for FNS. The neuroradiologist must accurately diagnose and characterize this lesion, and thus facilitate optimal preoperative planning and counseling. Laryngoscope, 2009
Energy output reduction and surface alteration of quartz and sapphire tips following Er:YAG laser contact irradiation for tooth enamel ablation
Authors: Eguro Toru , Aoki Akira , Maeda Toru , Takasaki Aristeo Atsushi , Hasegawa Mitsuru , Ogawa Masaaki , Suzuki Takanori , Yonemoto Kazuaki , Ishikawa Isao , Izumi Yuichi , Katsuumi Ichiroh
Published: September 2009

Background

Despite the recent increase in application of Er:YAG laser for various dental treatments, limited information is available regarding the contact tips. This study examined the changes in energy output and surface condition of quartz and sapphire contact tips after Er:YAG laser contact irradiation for tooth enamel ablation.

Materials and Methods

Ten sets of unused quartz or sapphire contact tips were employed for contact irradiation to sound enamel of extracted teeth. The teeth were irradiated with Er:YAG laser at approximately 75 J/cm2/pulse and 20 Hz under water spray for 60 minutes. The energy output was measured before and every 5 minutes after irradiation, and the changes in morphology and chemical composition of the contact surface were analyzed.

Results

The energy output significantly decreased with time in both tips. The energy output from the sapphire tips was generally higher on average than that of the quartz. The contact surfaces of all the used quartz tips were concave and irregular. Most of the sapphire tips also appeared rough with crater formation and fractures, except for a few tips in which a high energy output and the original smooth surface were maintained. Spots of melted tooth substances were seen attached to the surface of both tips.

Conclusion

In contact enamel ablation, the sapphire tip appeared to be more resistant than the quartz tip. The quartz tips showed similar patterns of energy reduction and surface alteration, whereas the sapphire tips revealed a wider and more characteristic variation among tips. Lasers Surg. Med. 41:595–604, 2009. © 2009 Wiley‐Liss, Inc.
Manipulation of Electrostatic and Saccharide Linker Interactions in the Design of Efficient Glycopolypeptide‐Based Cholera Toxin Inhibitors
Authors: Maheshwari Ronak , Levenson Eric A. , Kiick Kristi L.
Published: September 2009

Multivalent, glycopolymer inhibitors designed for the treatment of disease and pathogen infection have shown improvements in binding correlated with general changes in glycopolymer architecture and composition. We have previously demonstrated that control of glycopolypeptide backbone extension and ligand spacing significantly impacts the inhibition of the cholera toxin B subunit pentamer (CT B5) by these polymers. In the studies reported here, we elucidate the role of backbone charge and linker length in modulating the inhibition event. Peptides of the sequence AXPXG (where X is a positive, neutral or negative amino acid), equipped with the alkyne functionality of propargyl glycine, were designed and synthesized via solid‐phase peptide synthetic methods and glycosylated via Cu(I)‐catalyzed alkyne‐azide cycloaddition reactions. The capacity of the glycopeptides to inhibit the binding of the B5 subunit of cholera toxin was evaluated. These studies indicated that glycopeptides with a negatively charged backbone show improved inhibition of the binding event relative to the other glycopeptides. In addition, variations in the length of the linker between the peptide and the saccharide ligand also affected the inhibition of CT by the glycopeptides. Our findings suggest that, apart from appropriate saccharide spacing and polypeptide chain extension, saccharide linker conformation and the systematic placement of charges on the polypeptide backbone are also significant variables that can be tuned to improve the inhibitory potencies of glycopolypeptide‐based multivalent inhibitors.

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Synthesis of Di‐block Copolymers Containing Regioregular Poly(3‐hexylthiophene) and Poly(tetrahydrofuran) by a Combination of Grignard Metathesis and Cationic Polymerizations
Authors: Alemseghed Mussie G. , Gowrisanker Srinivas , Servello John , Stefan Mihaela C.
Published: September 2009

Poly(3‐hexylthiophene)‐block‐poly(tetrahydrofuran) was synthesized by cationic ring‐opening polymerization of tetrahydrofuran (THF) using a poly(3‐hexylthiophene) macroinitiator. Poly(3‐hexylthiophene) macroinitiator used for the ring‐opening polymerization of THF was synthesized by reacting the hydroxypropyl end‐group with trifluoromethanesulfonic anhydride in the presence of 2,6‐di‐tert‐butylpyridine. 1H NMR spectroscopy and SEC data confirmed the formation of the di‐block copolymers. Field‐effect mobility of poly(3‐hexylthiophene)‐block‐poly(tetrahydrofuran) was measured in a thin‐film transistor configuration and was found to be 0.009 cm2 · V−1 · s−1.

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The Effects of Binding Ligand Variation on the Nickel Catalyzed Externally Initiated Polymerization of 2‐Bromo‐3‐hexyl‐5‐iodothiophene
Authors: Doubina Natalia , Stoddard Michelina , Bronstein Hugo A. , Jen Alex K.‐Y. , Luscombe Christine K.
Published: September 2009

The effects of binding ligand variation on the externally initiated Ni catalyzed polymerization of P3HT were investigated using a novel methodology allowing facile screening of ligands. P3HT was synthesized with >80% initiator incorporation for both mono‐ and bidentate phosphine ligands. Variation of the initiating aryl group demonstrated vastly superior results for o‐tolyl over p‐tolyl substituents.

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Chain Transfer to Polymer and Branching in Controlled Radical Polymerizations of n‐Butyl Acrylate
Authors: Ahmad Nasir M. , Charleux Bernadette , Farcet Céline , Ferguson Christopher J. , Gaynor Scott G. , Hawkett Brian S. , Heatley Frank , Klumperman Bert , Konkolewicz Dominik , Lovell Peter A. , Matyjaszewski Krzysztof , Venkatesh Rajan
Published: September 2009

Chain transfer to polymer (CTP) in conventional free‐radical polymerizations (FRPs) and controlled radical polymerizations (ATRP, RAFT and NMP) of n‐butyl acrylate (BA) has been investigated using 13C NMR measurements of branching in the poly(n‐butyl acrylate) produced. The mol‐% branches are reduced significantly in the controlled radical polymerizations as compared to conventional FRPs. Several possible explanations for this observation are discussed critically and all except one refuted. The observations are explained in terms of differences in the concentration of highly reactive short‐chain radicals which can be expected to undergo both intra‐ and inter‐molecular CTP at much higher rates than long‐chain radicals. In conventional FRP, the distribution of radical concentrations is broad and there always is present a significant proportion of short‐chain radicals, whereas in controlled radical polymerizations, the distribution is narrow with only a small proportion of short‐chain radicals which diminishes as the living chains grow. Hence, irrespective of the type of control, controlled radical polymerizations give rise to lower levels of branching, when performed under otherwise similar conditions to conventional FRP. Similar observations are expected for other acrylates and monomers that undergo chain transfer to polymer during radical polymerization.

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Self‐Assembled Micelles Based on PEG‐Polypeptide Hybrid Copolymers for Drug Delivery
Authors: Hua Shou‐Hu , Li Yong‐Yong , Liu Yun , Xiao Wang , Li Cao , Huang Fu‐Wei , Zhang Xian‐Zheng , Zhuo Ren‐Xi
Published: September 2009

A series of amphiphilic poly(L‐leucine)‐block‐poly(ethylene glycol)‐block‐poly(L‐leucine) (PLL‐PEG‐PLL) hybrid triblock copolymers have been synthesized. All the blocks in this system have good biocompatibility and low toxicity. The PLL‐PEG‐PLL copolymers could self‐assemble into micelles with PLL blocks as the hydrophobic core and PEG blocks as the hydrophilic shell, which were characterized by FT‐IR, 1H NMR, and transmission electron microscopy analysis. The critical micellar concentration of the copolymer was 95.0 mg · L−1. The circular dichroism spectrum shows that the PLL segments adopt a unique α‐helical conformation, which is found to play an important role in controlling the drug release rate. The drug release could be effectively sustained by encapsulation in the micelles. The copolymers may have potential applications in drug delivery.

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On the Phase Nature of Polymer Brush Collapse upon Solvent Deterioration
Authors: Amoskov Victor M. , Birshtein Tatiana M.
Published: September 2009

The phase nature of polymer brush collapse upon deterioration of the solvent was investigated. The analysis is based on the self‐consistent field theory and the Flory‐Huggins model. It was shown that the transition from good to poor solvent via the θ‐point is actually a phase transition of high order. This result contradicts the conventional view on this process as a non‐phase one. According to the Ehrenfest classification, this process appears to be a fifth‐order phase transition.

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Hard versus Soft Materials as Supports for Metallocene and Post‐Metallocene Catalysts
Authors: Naundorf Corinna , Ferrari Daniela , Rojas Giovanni , Fink Gerhard , Klapper Markus , Müllen Klaus
Published: September 2009

The influence of organic supports on the polymerization behavior of post‐metallocene catalysts is studied and compared with similarly supported titanium and zirconium metallocenes. The effects of the immobilization, activation, and polymerization process were studied by video microscopy, laser confocal fluorescence microscopy, SEM, and TEM. A model for the polymerization process for a catalyst supported on latex particles was developed from the results obtained. Organic supports based on latex particles are easily adjustable for different catalysts due to the versatile functionalization of the surfaces and can be applied to different types of olefin polymerization catalysts. They can be considered as an alternative to SiO2 or MgCl2 supports.

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Quantitative 19F imaging of nmol‐level F‐nucleotides/‐sides from 5‐FU with T2 mapping in mice at 9.4T
Authors: Doi Yoshihiro , Shimmura Toshiyuki , Kuribayashi Hideto , Tanaka Yoshitsugu , Kanazawa Yoko
Published: September 2009

A unique acquisition method is proposed for quantitative, high‐sensitivity 19F MR spectroscopic imaging for the study of drug distribution aiming at nmol‐level metabolite information in mice. The use of fast spin echo (FSE) at 9.4T allowed us to obtain whole‐body images with minimal effect of magnetic susceptibility and to acquire several metabolite signals simultaneously by the method of interleaved multifrequency selection. Modified 2‐shot FSE was designed for simultaneous, high‐sensitivity 19F imaging and T2 mapping. A time course study including all the main metabolites at 10‐minute resolution was attained with an oral dose of 1–2 mmol 5‐fluorouracil (5‐FU) (130–260 mg)/kg in mice. With acquisition parameters optimized for in vivo T2 of 40 ms, images of F‐nucleotides/‐sides, effective anabolites of the anticancer drug 5‐FU, were obtained at the level of 200 nmol in the tumor for all the mice studied with a linear correlation (R = 0.96) between image intensity and the quantity determined in the excised tissue. The method exhibits potential capability of molecular imaging with a variety of 19F‐labeled compounds and drug evaluation. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
SENSE shimming (SSH): A fast approach for determining B0 field inhomogeneities using sensitivity coding
Authors: Splitthoff D.N. , Zaitsev M.
Published: September 2009

The pursuit of ever higher field strengths and faster data acquisitions has led to the construction of coil arrays with high numbers of elements. With the sensitivity encoding (SENSE) technique, it has been shown that the sensitivity of those elements can be used for spatial image encoding. Here, a proof‐of‐principle is presented of a method that can be considered an extreme case of the SENSE approach, completely abstaining from using encoding gradients. The resulting sensitivity encoded free‐induction decay (FID) data are then not used for imaging, but for determining B0 field inhomogeneity distribution. The method has therefore been termed “SENSE shimming” (SSH). In phantom experiments the method's ability to detect inhomogeneities of up to the second order is demonstrated. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Whole‐heart imaging using undersampled radial phase encoding (RPE) and iterative sensitivity encoding (SENSE) reconstruction
Authors: Boubertakh R. , Prieto C. , Batchelor P.G. , Uribe S. , Atkinson D. , Eggers H. , Sørensen T.S. , Hansen M.S. , Razavi R.S. , Schaeffter T.
Published: September 2009

Whole‐heart isotropic nonangulated cardiac magnetic resonance (CMR) is becoming an important protocol in simplifying MRI, since it reduces the need of cumbersome planning of angulations. However the acquisition times of whole‐heart MRI are prohibitive due to the large fields of view (FOVs) and the high spatial resolution required for depicting small structures and vessels. To address this problem, we propose a three‐dimensional (3D) acquisition scheme that combines Cartesian sampling in the readout direction with an undersampled radial scheme in the phase‐encoding plane. Different undersampling patterns were investigated in combination with an iterative sensitivity encoding (SENSE) reconstruction and a 32‐channel cardiac coil. Noise amplification maps were calculated to compare the performance of the different patterns using iterative SENSE reconstruction. The radial phase‐encoding (RPE) scheme was implemented on a clinical MR scanner and tested on phantoms and healthy volunteers. The proposed method exhibits better image quality even for high acceleration factors (up to 12) in comparison to Cartesian acquisitions. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Improved SNR efficiency in gradient echo coronary MRA with high temporal resolution using parallel imaging
Authors: Yu Jing , Schär Michael , Vonken Evert‐Jan , Kelle Sebastian , Stuber Matthias
Published: September 2009

Contemporary coronary magnetic resonance angiography techniques suffer from signal‐to‐noise ratio (SNR) constraints. We propose a method to enhance SNR in gradient echo coronary magnetic resonance angiography by using sensitivity encoding (SENSE). While the use of sensitivity encoding to improve SNR seems counterintuitive, it can be exploited by reducing the number of radiofrequency excitations during the acquisition window while lowering the signal readout bandwidth, therefore improving the radiofrequency receive to radiofrequency transmit duty cycle. Under certain conditions, this leads to improved SNR. The use of sensitivity encoding for improved SNR in three‐dimensional coronary magnetic resonance angiography is investigated using numerical simulations and an in vitro and an in vivo study. A maximum 55% SNR enhancement for coronary magnetic resonance angiography was found both in vitro and in vivo, which is well consistent with the numerical simulations. This method is most suitable for spoiled gradient echo coronary magnetic resonance angiography in which a high temporal and spatial resolution is required. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Metabolite proton T2 mapping in the healthy rhesus macaque brain at 3 T
Authors: Liu Songtao , Gonen Oded , Fleysher Roman , Fleysher Lazar , Babb James S. , Soher Brian J. , Joo Chan‐Gyu , Ratai Eva‐Maria , González R. Gilberto
Published: September 2009

The structure and metabolism of the rhesus macaque brain, an advanced model for neurologic diseases and their treatment response, is often studied noninvasively with MRI and 1H‐MR spectroscopy. Due to the shorter transverse relaxation time (T2) at the higher magnetic fields these studies favor, the echo times used in 1H‐MR spectroscopy subject the metabolites to unknown T2 weighting, decreasing the accuracy of quantification which is key for inter‐ and intra‐animal comparisons. To establish the “baseline” (healthy animal) T2 values, we mapped them for the three main metabolites' T2s at 3 T in four healthy rhesus macaques and tested the hypotheses that their mean values are similar (i) among animals; and (ii) to analogs regions in the human brain. This was done with three‐dimensional multivoxel 1H‐MR spectroscopy at (0.6 × 0.6 × 0.5 cm)3 = 180 μL spatial resolution over a 4.2 × 3.0 × 2.0 = 25 cm3 (∼30%) of the macaque brain in a two‐point protocol that optimizes T2 precision per unit time. The estimated T2s in several gray and white matter regions are all within 10% of those reported in the human brain (mean ± standard error of the mean): N‐acetylaspartate = 316 ± 7, creatine = 177 ± 3, and choline = 264 ± 9 ms, with no statistically significant gray versus white matter differences. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Maximum linear‐phase spectral‐spatial radiofrequency pulses for fat‐suppressed proton resonance frequency–shift MR Thermometry
Authors: Grissom William A. , Kerr Adam B. , Holbrook Andrew B. , Pauly John M. , Butts‐Pauly Kim
Published: September 2009

Conventional spectral‐spatial pulses used for water‐selective excitation in proton resonance frequency–shift MR thermometry require increased sequence length compared to shorter wideband pulses. This is because spectral‐spatial pulses are longer than wideband pulses, and the echo time period starts midway through them. Therefore, for a fixed echo time, one must increase sequence length to accommodate conventional spectral‐spatial pulses in proton resonance frequency–shift thermometry. We introduce improved water‐selective spectral‐spatial pulses for which the echo time period starts near the beginning of excitation. Instead of requiring increased sequence length, these pulses extend into the long echo time periods common to PRF sequences. The new pulses therefore alleviate the traditional tradeoff between sequence length and fat suppression. We experimentally demonstrate an 11% improvement in frame rate in a proton resonance frequency imaging sequence compared to conventional spectral‐spatial excitation. We also introduce a novel spectral‐spatial pulse design technique that is a hybrid of previous model‐ and filter‐based techniques and that inherits advantages from both. We experimentally validate the pulses' performance in suppressing lipid signal and in reducing sequence length compared to conventional spectral‐spatial pulses. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Quantification of non–water‐suppressed MR spectra with correction for motion‐induced signal reduction
Authors: Lin Jyh‐Miin , Tsai Shang‐Yueh , Liu Hua‐Shan , Chung Hsiao‐Wen , Mulkern Robert V. , Cheng Chou‐Min , Yeh Tzu‐Chen , Chen Nan‐Kuei
Published: September 2009

Intrascan subject movement in clinical MR spectroscopic examinations may result in inconsistent water suppression that distorts the metabolite signals, frame‐to‐frame variations in spectral phase and frequency, and consequent reductions in the signal‐to‐noise ratio due to destructive averaging. Frame‐to‐frame phase/frequency corrections, although reported to be successful in achieving constructive averaging, rely on consistent water suppression, which may be difficult in the presence of intrascan motion. In this study, motion correction using non–water‐suppressed data acquisition is proposed to overcome the above difficulties. The time‐domain matrix‐pencil postprocessing method was used to extract water signals from the non–water‐suppressed spectroscopic data, followed by phase and frequency corrections of the metabolite signals based on information obtained from the water signals. From in vivo experiments on seven healthy subjects at 3.0 T, quantification of metabolites using the unsuppressed water signal as a reference showed improved correlation with water‐suppressed data acquired in the absence of motion (R2 = 0.9669; slope = 0.94). The metabolite concentrations derived using the proposed approach were in good agreement with literature values. Computer simulations under various degrees of frequency and phase variations further demonstrated robust performance of the time‐domain postprocessing approach. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Methods for metabolic evaluation of prostate cancer cells using proton and 13C HR‐MAS spectroscopy and [3‐13C] pyruvate as a metabolic substrate
Authors: Levin Yakir S. , Albers Mark J. , Butler Thomas N. , Spielman Daniel , Peehl Donna M. , Kurhanewicz John
Published: September 2009

Prostate cancer has been shown to undergo unique metabolic changes associated with neoplastic transformation, with associated changes in citrate, alanine, and lactate concentrations. 13C high resolution‐magic angle spinning (HR‐MAS) spectroscopy provides an opportunity to simultaneously investigate the metabolic pathways implicated in these changes by using 13C‐labeled substrates as metabolic probes. In this work, a method to reproducibly interrogate metabolism in prostate cancer cells in primary culture was developed using HR‐MAS spectroscopy. Optimization of cell culture protocols, labeling parameters, harvesting, storage, and transfer was performed. Using [3‐13C] pyruvate as a metabolic probe, 1H and 13C HR‐MAS spectroscopy was used to quantify the net amount and fractional enrichment of several labeled metabolites that evolved in multiple cell samples from each of five different prostate cancers. Average enrichment across all cancers was 32.4 ± 5.4% for [3‐13C] alanine, 24.5 ± 5.4% for [4‐13C] glutamate, 9.1 ± 2.5% for [3‐13C] glutamate, 25.2 ± 5.7% for [3‐13C] aspartate, and 4.2 ± 1.0% for [3‐13C] lactate. Cell samples from the same parent population demonstrated reproducible fractional enrichments of alanine, glutamate, and aspartate to within 12%, 10%, and 10%, respectively. Furthermore, the cells produced a significant amount of [4‐13C] glutamate, which supports the bioenergetic theory for prostate cancer. These methods will allow further characterization of metabolic properties of prostate cancer cells in the future. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Inverse reconstruction method for segmented multishot diffusion‐weighted MRI with multiple coils
Authors: Uecker Martin , Karaus Alexander , Frahm Jens
Published: September 2009

Each k‐space segment in multishot diffusion‐weighted MRI is affected by a different spatially varying phase which is caused by unavoidable motions and amplified by the diffusion‐encoding gradients. A proper image reconstruction therefore requires phase maps for each segment. Such maps are commonly derived from two‐dimensional navigators at relatively low resolution but do not offer robust solutions. For example, phase variations in diffusion‐weighted MRI of the brain are often characterized by high spatial frequencies. To overcome this problem, an inverse reconstruction method for segmented multishot diffusion‐weighted MRI is described that takes advantage of the full k‐space data acquired from multiple receiver coils. First, the individual coil sensitivities are determined from the non–diffusion‐weighted acquisitions by regularized nonlinear inversion. These coil sensitivities are then used to estimate accurate motion‐associated phase maps for each segment by iterative linear inversion. Finally, the coil sensitivities and phase maps serve to reconstruct artifact‐free images of the object by iterative linear inversion, taking advantage of the data of all segments. The efficiency of the new method is demonstrated for segmented diffusion‐weighted stimulated echo acquisition mode MRI of the human brain. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Enhanced positive‐contrast visualization of paramagnetic contrast agents using phase images
Authors: Mills Parker H. , Ahrens Eric T.
Published: September 2009

Iron oxide–based MRI contrast agents are increasingly being used to noninvasively track cells, target molecular epitopes, and monitor gene expression in vivo. Detecting regions of contrast agent accumulation can be challenging if resulting contrast is subtle relative to endogenous tissue hypointensities. A postprocessing method is presented that yields enhanced positive‐contrast images from the phase map associated with T2*‐weighted MRI data. As examples, the method was applied to an agarose gel phantom doped with superparamagnetic iron‐oxide nanoparticles and in vivo and ex vivo mouse brains inoculated with recombinant viruses delivering transgenes that induce overexpression of paramagnetic ferritin. Overall, this approach generates images that exhibit a 1‐ to 8‐fold improvement in contrast‐to‐noise ratio in regions where paramagnetic agents are present compared to conventional magnitude images. This approach can be used in conjunction with conventional T2* pulse sequences, requires no prescans or increased scan time, and can be applied retrospectively to previously acquired data. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.