bluuebunny/crossref_metadata_2025_split huggingface dataset:
MR elastography of breast lesions: Understanding the solid/liquid duality can improve the specificity of contrast‐enhanced MR mammography
Authors: Sinkus Ralph , Siegmann Katja , Xydeas Tanja , Tanter Mickael , Claussen Claus , Fink Mathias 
Published: October 2007

AbstractThe purpose of this analysis is to explore the potential diagnostic gain provided by the viscoelastic shear properties of breast lesions for the improvement of the specificity of contrast enhanced dynamic MR mammography (MRM). The assessment of viscoelastic properties is done via dynamic MR elastography (MRE) and it is demonstrated that the complex shear modulus of in vivo breast tissue follows within the frequency range of clinical MRE a power law behavior. Taking benefit of this frequency behavior, data are interpreted in the framework of the exact model for wave propagation satisfying the causality principle. This allows to obtain the exponent of the frequency power law from the complex shear modulus at one single frequency which is validated experimentally. Thereby, scan time is drastically reduced. It is observed that malignant tumors obtain larger exponents of the power law than benign tumors indicating a more liquid‐like behavior. The combination of the Breast Imaging Reporting and Data System (BIRADS) categorization obtained via MRM with viscoelastic information leads to a substantial rise in specificity. Analysis of 39 malignant and 29 benign lesions shows a significant diagnostic gain with an increase of about 20% in specificity at 100% sensitivity. Magn Reson Med, 2007. © 2007 Wiley‐Liss, Inc.
Fast multislice mapping of the myelin water fraction using multicompartment analysis of T decay at 3T: A preliminary postmortem study
Authors: Du Yiping P. , Chu Renxin , Hwang Dosik , Brown Mark S. , Kleinschmidt‐DeMasters Bette K. , Singel Debra , Simon Jack H. 
Published: October 2007

AbstractQuantitative mapping of the myelin water content can provide significant insight into the pathophysiology of several white matter diseases, such as multiple sclerosis and leukoencephalopathies, and can potentially become a useful clinical tool for early diagnosis of these diseases. In this study, multicompartment analysis of T decay (MCAT2*) was used for the quantitative mapping of myelin water fraction (MWF). T decay of each voxel at multiple slice locations was acquired in fixed human brains using a multigradient‐echo (MGRE) pulse sequence with alternating readout gradient polarities. Compared to prior techniques using Carr‐Purcell‐Meiboom‐Gill (CPMG) acquisition, the MGRE acquisition approach has: 1) a very short first echo time (≈2 ms) and echo‐spacing (≈1 ms), which allows for the acquisition of multiple sampling points during the fast decay of the myelin water signal; 2) a low RF duty cycle, which is especially important for achieving acceptable specific absorption rate (SAR) levels at high field strengths. Multicompartment analysis was then applied to the T decay in each pixel using a 3‐pool model of white matter to detect the signal arising from the myelin water, myelinated axonal water, and mixed water compartments. Magn Reson Med 58:865–870, 2007. © 2007 Wiley‐Liss, Inc.
Minimizing RF heating of conducting wires in MRI
Authors: Yeung Christopher J. , Karmarkar Parag , McVeigh Elliot R. 
Published: October 2007

AbstractPerforming interventions using long conducting wires in MRI introduces the risk of focal RF heating at the wire tip. Comprehensive EM simulations are combined with carefully measured experimental data to show that method‐of‐moments EM field modeling coupled with heat transfer modeling can adequately predict RF heating with wires partially inserted into the patient‐mimicking phantom. The effects of total wire length, inserted length, wire position in the phantom, phantom position in the scanner, and phantom size are examined. Increasing phantom size can shift a wire's length of maximum tip heating from about a half wave toward a quarter wave. In any event, with wires parallel to the scanner bore, wire tip heating is minimized by keeping the patient and wires as close as possible to the central axis of the scanner bore. At 1.5T, heating is minimized if bare wires are shorter than 0.6 m or between ≈2.4 m and ≈3.0 m. Heating is further minimized if wire insertion into phantoms equivalent to most aqueous soft tissues is less than 13 cm or greater than 40 cm (longer for fatty tissues, bone, and lung). The methods demonstrated can be used to estimate the absolute amount of heating in order to set RF power safety thresholds. Magn Reson Med 58:1028–1034, 2007. © 2007 Wiley‐Liss, Inc.
Enhanced spectral shaping in steady‐state free precession imaging
Authors: Çukur Tolga , Bangerter Neal K. , Nishimura Dwight G. 
Published: October 2007

AbstractBalanced steady‐state free precession (SSFP) is hindered by the inherent off‐resonance sensitivity and unwanted bright fat signal. Multiple‐acquisition SSFP combination methods, where multiple datasets with different fixed RF phase increments are acquired, have been used for shaping the SSFP spectrum to solve both problems. We present a new combination method (weighted‐combination SSFP or WC‐SSFP) that preserves SSFP contrast and enables banding‐reduction and fat‐water separation. Methods addressing the banding artifact have focused on either getting robust banding‐reduction (complex‐sum SSFP) or improved SNR efficiency (sum‐of‐squares SSFP). The proposed method achieves both robust banding‐reduction and an SNR efficiency close to that of the sum‐of‐squares method. A drawback of fat suppression methods that create a broad stop‐band around the fat resonance is the wedge shape of the stop‐band leading to imperfect suppression. WC‐SSFP improves the suppression of the stop‐band without affecting the pass‐band performance, and prevents fat signal from obscuring the tissues of interest in the presence of considerable resonant frequency variations. The method further facilitates the use of SSFP imaging by providing a control parameter to adjust the level of banding‐reduction or fat suppression to application‐specific needs. Magn Reson Med, 2007. © 2007 Wiley‐Liss, Inc.
Morphing steady‐state free precession
Authors: Bieri O. , Patil S. , Quick H.H. , Scheffler K. 
Published: October 2007

AbstractA novel concept for visualization of positive contrast originating from susceptibility‐related magnetic field distortions is presented. In unbalanced steady‐state free precession (SSFP) the generic, gradient‐induced dephasing competes with local gradient fields generated by paramagnetic materials. Thus, within the same image, SSFP may morph its own appearance from unbalanced to balanced SSFP (bSSFP) as a result of local gradient compensation. In combination with low to very low flip angles, unbalanced SSFP signals are heavily suppressed, whereas bSSFP locally produces very high steady‐state amplitudes at certain frequency offsets. As a result, bSSFP signals appear hyperintense on an almost completely dark background. In this study, the conceptual issues of local gradient compensation and frequency matching, as well as the feasibility of proper detection of marker materials for interventional MRI from hyperintense pixels locations, are evaluated both in vitro and in vivo. Signal dependencies of morphing SSFP on sequence parameters such as flip angle or repetition time are investigated theoretically and experimentally. In addition to passive tracking of interventional devices, morphing SSFP might also be a promising new concept for the generation of positive contrast from super‐paramagnetic iron oxide (SPIO) particles in contrast‐enhanced MRI as well as for particle tracking. Magn Reson Med, 2007. © 2007 Wiley‐Liss, Inc.
Nanostructured Carbonized Thin Films Produced by Plasma Immersion Ion Implantation of Block‐Copolymer Assemblies
Authors: Kondyurin Alexey , Bilek Marcela , Janke Andreas , Stamm Manfred , Luchnikov Valeriy 
Published: October 2007

AbstractWe present a new approach for the fabrication of highly ordered carbonized nanostructured thin films involving the ion beam treatment of self‐assembled block copolymers precursors. 70 nm‐thick porous polystyrene‐block‐poly(4‐vinyl pyridine) assemblies were treated by 20 keV nitrogen ions at fluences of 1015–1016 ions · cm−2. The resulting 35 nm‐thick films are almost completely carbonized, as confirmed by FTIR and micro‐Raman spectra, and retain hexagonal nanomorphology. The films are mechanically robust, stable at high temperatures and well suited for applications as ultrafiltration membranes, quantum dot or single molecule supports, masks for nanolithography. The carbonization of the films due to ion beam exposure occurred at temperatures much lower than required for pyrolytic carbonization.magnified image
Methadone‐induced respiratory depression in the neonatal guinea pig
Authors: Nettleton Rosemary T. , Ransom Ty A. , Abraham Stephanie L. , Nelson Cole S. , Olsen George D. 
Published: October 2007

AbstractRespiratory depression, the most serious side‐effect of opioid treatment, is well documented for morphine, the most commonly used opioid in neonatal care. Less is known about methadone, a clinically relevant opioid analgesic, especially during neonatal development. This study was undertaken to determine the neonatal respiratory effects of methadone. We hypothesize that methadone is equipotent to morphine, compared to our previous morphine results in the same animal model, but has a much longer duration of action, due to its longer elimination half‐life. Neonatal guinea pigs (3–14 days old) randomly received a single subcutaneous dose of methadone or saline. Using a non‐invasive plethysmographic method, we measured ventilatory and metabolic parameters before injection and at intervals for 32 hr after injection while pups breathed “room air” or 5% CO2gas mixtures. Methadone‐induced depression of ventilation was most evident during 5% CO2challenge. The onset of drug effects was within 15 min for all ages and doses, but the duration of action decreased with age. While the depth of methadone‐induced respiratory depression did not depend on pup age, the control of breathing was different in 3‐day‐old pups, where inspiratory time increased fourfold; twice that of older pups. We conclude that methadone induces a naloxone reversible respiratory depression in guinea pig neonates and, in the very young, causes an abnormal breathing pattern due to changes in respiratory timing. Methadone is more potent than morphine with respect to neonatal respiratory depression, but surprisingly, the duration of methadone action was not longer than morphine. Pediatr Pulmonol. 2007; 42:1134–1143. © 2007 Wiley‐Liss, Inc.
Chest physiotherapy during anesthesia for children with cystic fibrosis: Effects on respiratory function
Authors: Tannenbaum E. , Prasad S.A. , Dinwiddie R. , Main Eleanor 
Published: October 2007

AbstractBackgroundPhysiotherapists sometimes use elective surgical procedures for children with cystic fibrosis as an opportunity to perform physiotherapy treatments during anesthesia. These treatments theoretically facilitate direct endotracheal airway clearance and compensate for any post‐operative respiratory deterioration related to the anaesthetic and surgery.Materials, patients, and methodsChildren were randomized either to receive physiotherapy or not following anesthesia and intubation. Respiratory mechanics (Crs and Rrs), tidal volume, and peak inspiratory pressure (PIP) were measured immediately before and after physiotherapy. FEV1 was measured before and after surgery and post‐operative physiotherapy requirements were recorded.ResultsEighteen patients, mean age 12 years (range 2.8–15 years) were recruited, with nine in each group. Both groups showed a non‐significant decline in FEV1 the day after surgery compared with pre‐operative values (−5.8%: physiotherapy and −7.1%: control). Both PIP and Rrs increased significantly following physiotherapy (within‐ and between‐groups, P < 0.05). In addition, there was a significant within‐group reduction in Crs after physiotherapy which approached significance between‐groups (P = 0.07). There were no significant within‐ or between‐group differences in tidal volume following treatment in either group.ConclusionThe unanticipated decline in respiratory function immediately following physiotherapy was short‐lived and not discernible in longer term outcomes measured by FEV1 or physiotherapy requirements post‐operatively. If respiratory physiotherapy under anesthesia is considered necessary and the benefits of removing secretions are deemed to outweigh the short‐term risks, it may be necessary for the anaesthetist to consider modifying ventilatory support to counteract any short‐term negative effects of the treatment. Pediatr Pulmonol. 2007; 42:1152–1158. © 2007 Wiley‐Liss, Inc.
Alveolar, but not bronchial nitric oxide production is elevated in cystic fibrosis
Authors: Suri Ranjan , Paraskakis Emmanouil , Bush Andrew 
Published: October 2007

AbstractExhaled nitric oxide (NO) remains a promising non‐invasive marker for measuring inflammation in lung diseases. In cystic fibrosis (CF), exhaled NO measured at a single expiratory flow has been found to be normal or low. However, this measure cannot localize the anatomical site of NO production. The aims of this study were to apply a multiple‐flow NO analysis to compare alveolar NO concentration and bronchial NO flux in CF children with healthy controls. Twenty‐two children with CF and 17 healthy controls had exhaled NO measured at four different expiratory flows to calculate bronchial NO flux and alveolar NO concentration. Median (range) alveolar NO concentration was 2.2 (0.6–5.6) ppb for children with CF and 1.5 (0.4–2.6) ppb for healthy controls. Median (range) bronchial NO flux was 445 (64–1,256) pL/sec for children with CF and 509 (197–1,913) pL/sec for healthy controls. Children with CF had a significantly higher alveolar NO concentration, but no significant difference in bronchial NO flux compared to healthy children. In conclusion, children with CF have increased alveolar NO production, but not bronchial NO flux compared to healthy controls. The distal airway is a major site of inflammation in CF, and measuring alveolar NO may be a marker of distal inflammation in this disease. Pediatr Pulmonol. 2007;42:1215–1221. © 2007 Wiley‐Liss, Inc.
The relationship between flash point and LFL with application to hybrid mixtures
Authors: Prugh Richard W. 
Published: October 2007

AbstractThere usually is a significant difference between the flash point and the equilibrium liquid/vapor (“saturation”) temperature that corresponds to the lower flammable limit (LFL). This occurs because (1) the LFL is frequently not measured at the flash point temperature and (2) the LFL concentrations are typically for upward propagation of flame, whereas the flash point is obtained for downward propagation of flame, and upward propagation occurs at lower (“conservative”) concentrations. In this paper, guidance is given for “correcting” this difference. Since many “hybrid” mixtures of flammable vapors and combustible dusts occur at elevated temperatures (as in driers), it may be important that the effect of temperature on the LFL be taken into account.For several hybrid mixtures, there is a linear relationship between the dust concentration and the vapor concentration that is required to make the mixture explosible. This relationship is more readily visualized if vapor concentrations are expressed in terms of grams per cubic meter (g/m3) like dust concentrations. A linear relationship is observed when the deflagration indices (Kst and Kg) are about equal, with strong deviations if the indices differ significantly. Testing is advisable to establish the relationship with confidence. © 2007 American Institute of Chemical Engineers Process Saf Prog 2008
Coupled nanopillar waveguides optical properties and applications
Authors: Chigrin Dmitry N. , Zhukovsky Sergei V. , Lavrinenko Andrei V. , Kroha Johann 
Published: October 2007

AbstractIn this paper we review basic properties of coupled periodic and aperiodic nanopillar waveguides. A coupled nanopillar waveguide consists of several rows of periodically or aperiodically placed dielectric rods (pillars). In such a waveguide, light confinement is due to the total internal reflection, while guided modes dispersion is strongly affected by the waveguide structure. We present a systematic analysis of the optical properties of coupled nanopillar waveguides and discuss their possible applications for integrated optics. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tunable superprism effect in photonic crystals
Authors: Glöckler F. , Peters S. , Lemmer U. , Gerken M. 
Published: October 2007

AbstractWe present a review of the field of tunable superprism structures. Such structures enable an active tuning of the group propagation angle by combining the large angular dispersion near the bandgap of a photonic crystal with a tuning of the optical material properties. The tuning is significantly enhanced compared to the change of the group propagation angle in a bulk material allowing for compact devices on the sub‐millimeter scale. Tunable superprism structures can be employed for many key components of optical circuitry and optical communications. Controlled deflection or refraction of light as well as spatial beam switching are only some possible tasks such devices could accomplish. We give a survey of geometries, switching mechanisms, and materials that have been investigated theoretically or experimentally for tunable photonic bandgap (PBG) structures and tunable superprism structures. A detailed theoretical investigation is presented for all‐optical switching in a one‐dimensional tunable superprism structure employing an optically non‐linear organic material. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Lasing in dye‐doped chiral liquid crystals: influence of defect modes
Authors: Haase Wolfgang , Podgornov Fedor , Matsuhisa Yuko , Ozaki Masanori 
Published: October 2007

AbstractIn this paper, we present the results of our investigations on the lasing in dye doped chiral liquid crystals with structural defects. The introduction of structural defects (TiO2microbeads) into cholesterics results in multimode laser generation and increasing the threshold energy. In the same time, utilization of multilayers in a FLC cell leads to a tremendous reduction of threshold energy. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Preface: phys. stat. sol. (a) 204/11
Authors: Wehrspohn Ralf B. , Kitzerow Heinz‐Siegfried , Busch Kurt 
Published: October 2007

AbstractStimulated by the pioneering work of Sajeev John and Eli Yablonovitsch in 1987, German research groups started in the early 90s with theoretical and experimental work on 2D and 3D photonics crystals. This initial work was the basis of an application for a Priority Programme on Photonic Crystals at the German Science Foundation (DFG) in 1999. In the last seven years, a consortium consisting of more than 20 German research groups worked together in the area of photonic crystals.We started with linear, non‐dispersive properties of purely dielectric 2D and 3D photonic crystals in the late 90s and developed the field of research step‐by‐step to non‐linear and dispersive properties of dielectric photonic crystals including gain and/or losses. These properties where studied on different materials systems such as silicon, III–V‐compound semiconductors, oxides and polymers as well as hybrid systems consisting of dielectric photonic crystals and liquid crystals. Applications of these systems were developed in the area of active photonic crystals fibres, functional optical components as well as sensors. Some of them have even entered into industrial applications. During the funding period, some groups extended the initial focus to non‐dielectric, dispersive materials such as metals and discussed the properties of periodic metallic structures (plasmonic crystals). After the groundbreaking work of John Pendry at the beginning of this century, also resonances in dispersive structures with periodic permeability and permittivity (metamaterials) were studied. This was important to understand the difference of negative refraction in metamaterials and dielectric photonic crystals.This special issue summarizes the work of those groups being part of the German Priority Programme. Other groups not funded by this project but by other grants joined the German initiative on photonic crystals. Workshops of all groups working in the field have been carried out at the German Physical Society meeting every year. Our work was also stimulated by the numerous Humboldt Awardees which visited Germany in the last seven years such as Sajeev John, Costas Soukoulis, Thomas Krauss and many others. We are also pleased that some of our close collaborators over the last six years have contributed to this issue, Dan Davidovs group from the Hebrew University, Israel and Masanori Ozaki group from Osaka University, Japan.At the end of this project, photonic crystals, plasmonic materials and metamaterials have been established as mature research field in Germany. They entered the academic curriculum and several professorships have been denominated in this area so that our common research can continue in the future. We are deeply indebted to the German Science Foundation that they have supported this research field over the last seven years. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Constrained piecewise linear systems with disturbances: Controller designviaconvex invariant sets
Authors: Sui Dan , Ong Chong Jin 
Published: October 2007

AbstractThis paper presents two control strategies under the time optimal control and model predictive control frameworks for constrained piecewise linear systems with bounded disturbances (PWLBD systems). Each of the proposed approaches uses an inner convex polytopal approximation of the non‐convex domains of attraction and results in simplified control laws that can be determined off‐lineviamulti‐parametric programming. These control strategies rely on invariant sets of PWLBD systems. Thereby, approaches for the computation of the disturbance invariant outer bounds of the minimal disturbance invariant set,F∞, and convex polytopal disturbance invariant sets are presented. The effectiveness of the approaches is assessed through numerical examples. Copyright © 2007 John Wiley & Sons, Ltd.
On an online random k‐SAT model
Authors: Kravitz David 
Published: October 2007

AbstractGiven n Boolean variables x1,…,xn, a k‐clause is a disjunction of k literals, where a literal is a variable or its negation. Suppose random k‐clauses are generated one at a time and an online algorithm accepts or rejects each clause as it is generated. Our goal is to accept as many randomly generated k‐clauses as possible with the condition that it must be possible to satisfy every clause that is accepted. When cn random k‐clauses on n variables are given, a natural online algorithm known as Online‐Lazy accepts an expected (1 − ${{1}\over {2^{k}}}$)cn + akn clauses for some constant ak. If these clauses are given offline, it is possible to do much better, (1 − ${{1}\over {2^{k}}}$)cn + Ω($\sqrt{c}$)n can be accepted whp. The question of closing the gap between ak and Ω($\sqrt{c}$) for the online version remained open. This article shows that for any k ≥ 1, any online algorithm will accept less than (1 − ${{1}\over {2^{k}}}$)cn + (ln 2)n k‐clauses whp, closing the gap between the constant and Ω($\sqrt{c}$). Furthermore we show that this bound is asymptotically tight as k → ∞. © 2007 Wiley Periodicals, Inc. Random Struct. Alg., 2008