bluuebunny/crossref_metadata_2025 huggingface dataset:
The physical basis of model-free analysis of NMR relaxation data from proteins and complex fluids
Authors: Halle Bertil
Published: December 2009

NMR relaxation experiments have provided a wealth of information about molecular motions in macromolecules and ordered fluids. Even though a rigorous theory of spin relaxation is available, the complexity of the investigated systems often makes the interpretation of limited datasets challenging and ambiguous. To allow physically meaningful information to be extracted from the data without commitment to detailed dynamical models, several versions of a model-free (MF) approach to data analysis have been developed. During the past 2 decades, the MF approach has been used in the vast majority of all NMR relaxation studies of internal motions in proteins and other macromolecules, and it has also played an important role in studies of colloidal systems. Although the MF approach has been almost universally adopted, substantial disagreement remains about its physical foundations and range of validity. It is our aim here to clarify these issues. To this end, we first present rigorous derivations of the three well-known MF formulas for the time correlation function relevant for isotropic solutions. These derivations are more general than the original ones, thereby substantially extending the range of validity of the MF approach. We point out several common misconceptions and explain the physical significance of the approximations involved. In particular, we discuss symmetry requirements and the dynamical decoupling approximation that plays a key role in the MF approach. We also derive a new MF formula, applicable to anisotropic fluids and solids, including microcrystalline protein samples. The so-called slowly relaxing local structure (SRLS) model has been advanced as an alternative to the MF approach that does not require dynamical decoupling of internal and global motions. To resolve the existing controversy about the relative merits of the SRLS model and the MF approach, we formulate and solve a planar version of the SRLS model. The analytical solution of this model reveals the unphysical consequences of the symmetrical two-body Smoluchowski equation as applied to protein dynamics, thus refuting the widely held belief that the SRLS model is more accurate than the MF approach. The different results obtained by analyzing data with these two approaches therefore do not indicate the importance of dynamical coupling between internal and global motions. Finally, we explore the two principal mechanisms of dynamical coupling in proteins: torque-mediated and friction-mediated coupling. We argue by way of specific analytically solvable models that torque-mediated coupling (which the SRLS model attempts to capture) is unimportant because the relatively slow internal motions that might couple to the global motion tend to be intermittent (jumplike) in character, whereas friction-mediated coupling (which neither the SRLS model nor the MF approach incorporates) may be important for proteins with unstructured parts or flexibly connected domains.
Robust extremes in chaotic deterministic systems
Authors: Vitolo Renato , Holland Mark P. , Ferro Christopher A. T.
Published: December 2009

This paper introduces the notion of robust extremes in deterministic chaotic systems, presents initial theoretical results, and outlines associated inferential techniques. A chaotic deterministic system is said to exhibit robust extremes under a given observable when the associated statistics of extreme values depend smoothly on the system’s control parameters. Robust extremes are here illustrated numerically for the flow of the Lorenz model [E. N. Lorenz, J. Atmos. Sci. 20, 130 (1963)]. Robustness of extremes is proved for one-dimensional Lorenz maps with two distinct types of observables for which conditions guaranteeing robust extremes are formulated explicitly. Two applications are shown: improving the precision of the statistical estimator for extreme value distributions and predicting future extremes in nonstationary systems. For the latter, extreme wind speeds are examined in a simple quasigeostrophic model with a robust chaotic attractor subject to nonstationary forcing.
AlN/ZnO/diamond structure combining isolated and surface acoustic waves
Authors: Elmazria Omar , Zhgoon Sergei , Le Brizoual Laurent , Sarry Frédéric , Tsimbal Dmitry , Djouadi Mohammed Abdou
Published: December 2009

In order to generate surface acoustic waves (SAW) and waveguiding layer acoustic waves (WLAW) simultaneously, a multilayer structure of AlN/ZnO/diamond has been proposed. This structure has been investigated theoretically (two-dimensional finite element method) and experimentally. The nature of the excited modes and their order were identified by modeling and confirmed experimentally by measuring the frequency response of the device in the air and in contact with the liquid. The demonstrated structure can be used to realize a packageless sensor or resonator, using the WLAW alone. A temperature compensated gas or liquid sensor can also be realized by combined usage of the SAW and the WLAW.
Room temperature multiferroic properties of Nd:BiFeO3/Bi2FeMnO6 bilayered films
Authors: Zhao Hongyang , Kimura Hideo , Cheng Zhenxiang , Wang Xiaolin , Nishida Takashi
Published: December 2009

Nd 0.1 Bi 0.9 FeO 3 / Bi 2 FeMnO 6 bilayered films were deposited on Pt/Ti/SiO2/Si substrate by pulsed laser deposition method. BiFeO3 is antiferromagnet while BiMnO3 is ferromagnet, the ordering of –Mn–O–Fe–O–Mn– is expected, which will induce the ferromagnetic interation in the film. The film shows typical ferromagnetic properties with the transition temperature of Tc of 440 K. The room temperature (RT) ferroelectric polarization was also observed, suggesting that the film is a promising RT multiferroism.
Exact Kohn–Sham potential of strongly correlated finite systems
Authors: Helbig N. , Tokatly I. V. , Rubio A.
Published: December 2009

The dissociation of molecules, even the most simple hydrogen molecule, cannot be described accurately within density functional theory because none of the currently available functionals accounts for strong on-site correlation. This problem led to a discussion of properties that the local Kohn–Sham potential has to satisfy in order to correctly describe strongly correlated systems. We derive an analytic expression for the nontrivial form of the Kohn–Sham potential in between the two fragments for the dissociation of a single bond. We show that the numerical calculations for a one-dimensional two-electron model system indeed approach and reach this limit. It is shown that the functional form of the potential is universal, i.e., independent of the details of the two fragments.
Coercivity tuning in Co/Pd multilayer based bit patterned media
Authors: Hellwig O. , Hauet T. , Thomson T. , Dobisz E. , Risner-Jamtgaard J. D. , Yaney D. , Terris B. D. , Fullerton E. E.
Published: December 2009

In order to adjust the reversal field of high anisotropy [Co(2.8 Å)/Pd(9 Å)]8 bit patterned media (BPM), one may increase the individual Co thickness to change the overall anisotropy or alternatively combine the high anisotropy multilayer with a lower anisotropy material, thus creating a heterogeneous laminated system. In the current study, we find that [Co/Pd]8−N[Co/Ni]N hard-soft laminated BPM allows tuning the coercivity while maintaining a narrow normalized switching field distribution (σSFD/HC), whereas homogeneous structures with increased individual Co thickness show a more pronounced increase in σSFD/HC. Possible reasons for the different behavior, such as changes in strain and texture, are discussed.
Cavity pressure acceleration: An efficient laser-based method of production of high-velocity macroparticles
Authors: Borodziuk S. , Kasperczuk A. , Pisarczyk T. , Badziak J. , Chodukowski T. , Ullschmied J. , Krousky E. , Masek K. , Pfeifer M. , Rohlena K. , Skala J. , Pisarczyk P.
Published: December 2009

We propose an efficient method of accelerating macroparticles to high velocities, which employs pressure of the plasma produced by a focused pulsed high-power laser beam inside a cavity-type target. That is why we have called it the cavity pressure acceleration (CPA) scheme. The method was tested during our experiments at the Prague Asterix Laser System, the results of which are reported here. They show that CPA makes it possible to accelerate both light and heavy macroparticles in arbitrary direction, with the acceleration efficiency far exceeding that achieved upto now by using the classic ablative acceleration scheme. High velocities of the macroparticles (foil fragments) produced and possibility of accelerating even rather heavy macroparticles are promising from the point of view of impact fusion studies, of the impact fast ignition, in particular.
Trapping-detrapping fluctuations in organic space-charge layers
Authors: Carbone Anna , Pennetta Cecilia , Reggiani Lino
Published: December 2009

A trapping-detrapping model is proposed for explaining the current fluctuation behavior in organic semiconductors (polyacenes) operating under current-injection conditions. The fraction of ionized traps obtained from the current-voltage characteristics, is related to the relative current noise spectral density at the trap-filling transition. The agreement between theory and experiments validates the model and provides an estimate of the concentration and energy level of deep traps.
Relaxation characteristics of quantum-dash-based semiconductor lasers
Authors: Erneux Thomas , Viktorov Evgeny A. , Mandel Paul , Azouigui Sheherazade , Ramdane Abderrahim
Published: December 2009

We analyze the relaxation dynamics of quantum dot/dash lasers in terms of the energy exchange between the ground state and the wetting layer. We consider the case where both capture and escape times are of the same order of magnitude and determine the relaxation oscillation frequency and its damping rate. We show that the escape process may significantly affect the modulation characteristics and the tolerance to optical feedback.
Environment-dependent metastability of passivation-free indium zinc oxide thin film transistor after gate bias stress
Authors: Liu Po-Tsun , Chou Yi-Teh , Teng Li-Feng
Published: December 2009

We investigated the effects of bias stress on a passivation-free InZnO thin-film transistors (a-IZO TFTs) exposed to either the atmosphere or a vacuum. The magnitude of threshold voltage shift increased with the application duration of bias stress, to an extent that was much larger in the atmosphere than in the vacuum. The threshold voltage recovered slowly to its nearly initial value when the gate bias stress was removed. The electrical metastability was attributed to the interaction between the exposed a-IZO backchannel and oxygen/moisture from the atmosphere, and a dynamic equilibrium was finally achieved, regardless of the polarity of stress voltage.
Multiconfigurational time-dependent Hartree calculations for tunneling splittings of vibrational states: Theoretical considerations and application to malonaldehyde
Authors: Hammer Thorsten , Coutinho-Neto Mauricio D. , Viel Alexandra , Manthe Uwe
Published: December 2009

Full-dimensional multiconfigurational time-dependent Hartree calculations on the tunneling splitting of the vibrational ground state and the low lying excited states of malonaldehyde are presented. Methodological developments utilizing the symmetry of double well systems for the efficient calculation of tunneling splittings are described and discussed. Important aspects of the theory underlying the previously communicated results for the ground state tunneling splitting [M. D. Coutinho-Neto et al., J. Chem. Phys. 121, 9207 (2004)] are detailed and further developments facilitating the calculation of tunneling splittings for vibrationally excited states are introduced. Utilizing these developments, the 14 lowest vibrational states of malonaldehyde, i.e., seven tunneling splittings, have been computed. The tunneling splittings are found to vary significantly depending on the particular vibrational excitation. This results in a complex pattern of vibrational levels. Studying the dependence of the tunneling splittings on the vibrational excitation, good agreement with available experimental results is found and intuitive interpretations of the results can be given.
An approach to operational forest fire growth predictions for Canada
Authors: Anderson K. R. , Englefield P. , Little J. M. , Reuter Gerhard
Published: December 2009

This paper presents an operational approach to predicting fire growth for wildland fires in Canada. The approach addresses data assimilation to provide predictions in a timely and efficient manner. Fuels and elevation grids, forecast weather, and active fire locations are entered into a fire-growth model; then predicted fire perimeters are mapped and presented on the web. The Moderate Resolution Imaging Spectroradiometer (MODIS) and the National Oceanic and Atmospheric Administration Advanced Very High Resolution Radiometer (NOAA/AVHRR) satellite-based detection systems are used to detect current wildland fires (referred to as hotspots). For selected regions, fire-growth simulation environments are assembled. Fuel type data from several fire management agencies are available in grid format at a resolution of 100 m or less; in areas where such data are not available, a national fuels map based on Satellite Pour l’Observation de la Terre Vegetation sensor (SPOT VGT) land cover and forest inventory is used. Similarly, terrain data are available from a variety of sources. Current hotspots are used as ignition points while past hotspots are used to delineate area burned. Surface wind, temperature, and dew-point values (forecast by Environment Canada) are used to determine the fire weather conditions at the fire location. A case study of two large fires in Canada consisting of 54 fire simulation days is used to test these hypotheses.
Effects of targeted cattle grazing on fire behavior of cheatgrass-dominated rangeland in the northern Great Basin, USA
Authors: Diamond Joel M. , Call Christopher A. , Devoe Nora
Published: December 2009

We evaluated the effectiveness of using targeted, or prescribed, cattle grazing to reduce the flame length and rate of spread of fires on cheatgrass (Bromus tectorum)-dominated rangeland in northern Nevada. Cattle removed 80–90% of B. tectorum biomass during the boot (phenological) stage in grazed plots in May 2005. Grazed and ungrazed plots were burned in October 2005 to assess fire behavior characteristics. Targeted grazing reduced B. tectorum biomass and cover, which resulted in reductions in flame length and rate of spread. When the grazing treatments were repeated on the same plots in May 2006, B. tectorum biomass and cover were reduced to the point that fires did not carry in the grazed plots in October 2006. Fuel characteristics of the 2005 burns were used to parameterize dry-climate grass models in BEHAVE Plus, and simulation modeling indicates that targeted grazing in spring (May) will reduce the potential for catastrophic fires during the peak fire season (July–August) in the northern Great Basin.
Deep sequencing analysis of the
Methanosarcina mazei
Gö1 transcriptome in response to nitrogen availability
Authors: Jäger Dominik , Sharma Cynthia M. , Thomsen Jens , Ehlers Claudia , Vogel Jörg , Schmitz Ruth A.
Published: December 2009

Methanosarcina mazei
and related mesophilic
archaea
are the only organisms fermenting acetate, methylamines, and methanol to methane and carbon dioxide, contributing significantly to greenhouse gas production. The biochemistry of these metabolic processes is well studied, and genome sequences are available, yet little is known about the overall transcriptional organization and the noncoding regions representing 25% of the 4.01-Mb genome of
M. mazei
. We present a genome-wide analysis of transcription start sites (TSS) in
M. mazei
grown under different nitrogen availabilities. Pyrosequencing-based differential analysis of primary vs. processed 5′ ends of transcripts discovered 876 TSS across the
M. mazei
genome. Unlike in other archaea, in which leaderless mRNAs are prevalent, the majority of the detected mRNAs in
M. mazei
carry long untranslated 5′ regions. Our experimental data predict a total of 208 small RNA (sRNA) candidates, mostly from intergenic regions but also antisense to 5′ and 3′ regions of mRNAs. In addition, 40 new small mRNAs with ORFs of ≤30 aa were identified, some of which might have dual functions as mRNA and regulatory sRNA. We confirmed differential expression of several sRNA genes in response to nitrogen availability. Inspection of their promoter regions revealed a unique conserved sequence motif associated with nitrogen-responsive regulation, which might serve as a regulator binding site upstream of the common IIB recognition element. Strikingly, several sRNAs antisense to mRNAs encoding transposases indicate nitrogen-dependent transposition events. This global TSS map in archaea will facilitate a better understanding of transcriptional and posttranscriptional control in the third domain of life.
Activity-independent specification of synaptic targets in the posterior lateral line of the larval zebrafish
Authors: Nagiel Aaron , Patel Suchit H. , Andor-Ardó Daniel , Hudspeth A. J.
Published: December 2009

The development of functional neural circuits requires that connections between neurons be established in a precise manner. The mechanisms by which complex nervous systems perform this daunting task remain largely unknown. In the posterior lateral line of larval zebrafish, each afferent neuron forms synaptic contacts with hair cells of a common hair-bundle polarity. We investigated whether afferent neurons distinguish hair-cell polarities by analyzing differences in the synaptic signaling between oppositely polarized hair cells. By examining two mutant zebrafish lines with defects in mechanoelectrical transduction, and by blocking transduction during the development of wild-type fish, we found that afferent neurons could form specific synapses in the absence of stimulus-evoked patterns of synaptic release. Asking next whether this specificity arises through intrinsically generated patterns of synaptic release, we found that the polarity preference persisted in two mutant lines lacking essential synaptic proteins. These results indicate that lateral-line afferent neurons do not require synaptic activity to distinguish hair-cell polarities and suggest that molecular labels of hair-cell polarity guide prepatterned afferents to form the appropriate synapses.
Gli2 trafficking links Hedgehog-dependent activation of Smoothened in the primary cilium to transcriptional activation in the nucleus
Authors: Kim Jynho , Kato Masaki , Beachy Philip A.
Published: December 2009

Stimulation by the extracellular Hedgehog (Hh) protein signal has been shown to alter ciliary localization of the mammalian Hh receptor components Smoothened (Smo) and Patched (Ptc), and mutations that disrupt the structure and function of the cilium also disrupt Hh-induced changes in gene expression. But how ciliary events affect gene expression in the nucleus is not known, and to address this question we have characterized the cellular trafficking of Gli2, the principal mediator of Hh-dependent transcriptional activation. From a combination of pharmacological and genetic manipulations we find in resting cells that both Gli2 and Smo appear to shuttle in and out of the cilium, with Gli2 but not Smo requiring intact cytoplasmic microtubules for ciliary entry and both requiring the ciliary retrograde motor, cytoplasmic dynein 2, for ciliary exit. We also find that changes in ciliary and nuclear trafficking of Gli2 are triggered by the Hh-dependent accumulation of activated Smo in the cilium, resulting in a shift from primarily cytoplasmic localization to accumulation at the distal tip of the cilium and within the nucleus. Gli2 thus functions as a dynamic monitor of Smo activity in the cilium and thereby links Hh pathway activation in the cilium to transcriptional activation in the nucleus.
Dynamics of the Dorsal morphogen gradient
Authors: Kanodia Jitendra S. , Rikhy Richa , Kim Yoosik , Lund Viktor K. , DeLotto Robert , Lippincott-Schwartz Jennifer , Shvartsman Stanislav Y.
Published: December 2009

The dorsoventral (DV) patterning of the
Drosophila
embryo depends on the nuclear localization gradient of Dorsal (Dl), a protein related to the mammalian NF-κB transcription factors. Current understanding of how the Dl gradient works has been derived from studies of its transcriptional interpretation, but the gradient itself has not been quantified. In particular, it is not known whether the Dl gradient is stable or dynamic during the DV patterning of the embryo. To address this question, we developed a mathematical model of the Dl gradient and constrained its parameters by experimental data. Based on our computational analysis, we predict that the Dl gradient is dynamic and, to a first approximation, can be described as a concentration profile with increasing amplitude and constant shape. These time-dependent properties of the Dl gradient are different from those of the Bicoid and MAPK phosphorylation gradients, which pattern the anterior and terminal regions of the embryo. Specifically, the gradient of the nuclear levels of Bicoid is stable, whereas the pattern of MAPK phosphorylation changes in both shape and amplitude. We attribute these striking differences in the dynamics of maternal morphogen gradients to the differences in the initial conditions and chemistries of the anterior, DV, and terminal systems.
Book reviews
Authors: Smith H.‐J.
Published: December 2009

Clinical MR Imaging. A Practical Approach, 2nd completely revised and updated edition. Edited by P. Reimer, P. M. Parizel, F.-A. Stichnoth. Springer-Verlag 2003. ISBN 3-540-43467-4. 600 pages, 494 figures, 141 tables. Price hardcover: €99.95 (net).
Magnetic resonance cholangiopancreatography: image quality, ductal morphology, and value of additional T2‐ and T1‐weighted sequences for the assessment of suspected pancreatic cancer
Authors: Lopez Hänninen E. , Ricke J. , Amthauer H. , Röttgen R. , Böhmig M. , Langrehr J. , Pech M. , Denecke T. , Rosewicz S. , Felix R.
Published: December 2009

Purpose: To assess image quality and duct morphology on magnetic resonance cholangiopancreatography (MRCP) and also the value of additional T2‐ and T1‐weighted sequences for differentiation of benignity and malignancy in patients with suspected pancreatic tumors.

Material and Methods: One‐hundred‐and‐fourteen patients received MRCP and unenhanced and contrast material‐enhanced MR imaging. MR results were analyzed independently by two blinded readers, and subsequently correlated with the results from surgery, biopsy, and follow‐up. Assessment included the evaluation of image quality, duct visualization and morphology, and the differentiation of pancreatic lesion status (benign versus malignant).

Results: Overall, 49 patients had benign final diagnoses, while 65 had a malignant diagnosis. Image quality of single‐shot thick‐slab MRCP was rated significantly better than the MIP images of multisection MRCP. With MRCP alone, the two readers' accuracy in the assessment of pancreatic lesion status was 72% (95% CI, 64% to 83%) and 69% (95% CI, 56% to 77%), respectively; with the addition of T2‐ and T1‐weighted images the accuracy significantly improved to 89% (95% CI, 82% to 95%) and 84% (95% CI, 77% to 92%) for readers 1 and 2, respectively.

Conclusion: Single‐shot thick‐slab MRCP and multisection MRCP provide complementary results; however, single‐shot MRCP had superior image quality. Moreover, assessment of ductal morphology with MRCP alone facilitated the diagnosis of different pathologic conditions of the pancreatobiliary system in the majority of patients. However, with the addition of T2‐ and T1‐weighted sequences the overall diagnostic accuracy was significantly improved and thus we consider that a comprehensive MR approach should comprise both MRCP techniques and parenchymal sequences.
Sonographic comparison of gastric emptying of broth and water: is there a promoting cephalic factor?
Authors: Pedersen J. F.
Published: December 2009

Purpose: To examine the emptying times of broth and water, and explore the possibility of a cephalic influence on gastric emptying.

Material and Methods: On different days each of twelve healthy volunteers had meals of either 350 ml water or 350 ml broth. Subsequently ten volunteers had meals of water alone and of water followed by sham feeding with broth. The antral area was determined at sonography five times before the meal as a baseline, and every 1–4 minutes after the meal. The time until the antral area had decreased to 150% of baseline (T150) was determined and used as surrogate expression of gastric emptying time.

Results: The mean T150 was for water 20.3 min (range 12–40), and was for broth significantly shorter 12.6 min (5–21), P = 0.0020. In the subsequent series the mean T150 was 28.5 min (18–49) for water, and significantly shorter for water followed by sham feeding, 22.8 (14–40), P = 0.0078.

Conclusion: Broth empties faster from the stomach than plain water, probably because of a “cephalic phase” stimulation of gastric motility via the vagus nerve.
Colon dissection: a new three‐dimensional reconstruction tool for computed tomography colonography
Authors: Röttgen R. , Fischbach F. , Plotkin M. , Herzog H. , Freund T. , Schröder R. J. , Felix R.
Published: December 2009

Purpose: To improve the sensitivity of computed tomography (CT) colonography in the detection of polyps by comparing the 3D reconstruction tool “colon dissection” and endoluminal view (virtual colonoscopy) with axial 2D reconstructions.

Material and Methods: Forty‐eight patients (22 M, 26 F, mean age 57±21) were studied after intra‐anal air insufflation in the supine and prone positions using a 16‐slice helical CT (16×0.625 mm, pitch 1.7; detector rotation time 0.5 s; 160 mAs und 120 kV) and conventional colonoscopy. Two radiologists blinded to the results of the conventional colonoscopy analyzed the 3D reconstruction in virtual‐endoscopy mode, in colon‐dissection mode, and axial 2D slices.

Results: Conventional colonoscopy revealed a total of 35 polyps in 15 patients; 33 polyps were disclosed by CT methods. Sensitivity and specificity for detecting colon polyps were 94% and 94%, respectively, when using the “colon dissection”, 89% and 94% when using “virtual endoscopy”, and 62% and 100% when using axial 2D reconstruction. Sensitivity in relation to the diameter of colon polyps with “colon dissection”, “virtual colonoscopy”, and axial 2D‐slices was: polyps with a diameter >5.0 mm, 100%, 100%, and 71%, respectively; polyps with a diameter of between 3 and 4.9 mm, 92%, 85%, and 46%; and polyps with a diameter <3 mm, 89%, 78%, and 56%. The difference between “virtual endoscopy” and “colon dissection” in diagnosing polyps up to 4.9 mm in diameter was statistically significant.

Conclusion: 3D reconstruction software “colon dissection” improves sensitivity of CT colonography compared with the endoluminal view.
Magnetic resonance imaging findings in chronic carbon monoxide intoxication
Authors: Durak A. C. , Coskun A. , Yikilmaz A. , Erdogan F. , Mavili E. , Guven M.
Published: December 2009

Purpose: To define the cranial magnetic resonance imaging (MRI) features of the chronic stage of carbon monoxide (CO) poisoning in patients with and without neuropsychiatric sequelae.

Material and Methods: Eight patients who had neither symptoms nor neurological sequelae and eight patients with neuropsychiatric sequelae were included in the study. Patients aged between 9 to 57 (mean 32.2 years). All patients had been comatose at initial admittance and awoke after normobaric 100% oxygen therapy within 1–7 days. In this study, the patients were being examined with routine cranial MRI between 1 and 10 years (mean 3.4 years) after exposure to CO.

Results: The most common finding was bilateral symmetric hyperintensity of the white matter, which was more significant in the centrum semiovale, with relative sparing of the temporal lobes and anterior parts of the frontal lobes on T2‐weighted and FLAIR images in all patients. Cerebral cortical atrophy was seen in 10 patients; mild atrophy of cerebellar hemispheres in 8; and vermian atrophy in 11. Corpus callosum was atrophic in one patient. Bilateral globus pallidus lesions were seen in three patients. The lesions were hypointense on T1‐weighted images and hyperintense on T2‐weighted and FLAIR images.

Conclusion: Patients with severe CO intoxication may develop persistent cerebral changes independently of their neuropsychiatric findings in the chronic stage. They may present with characteristic MRI findings as described here, even if asymptomatic. The history of CO exposure is therefore helpful for recognizing and interpreting the MRI findings of chronic stage CO intoxication.
Infra‐inguinal percutaneous transluminal angioplasty for limb salvage: a retrospective analysis in a single center
Authors: Eskelinen E. , Albäck A. , Roth W‐D. , Lappalainen K. , Keto P. , Railo M. , Eskelinen A. , Lepäntalo M.
Published: December 2009

Purpose: To review the feasibility of infra‐inguinal angioplasty in the management of critical limb ischemia (CLI).

Material and Methods: Data on 221 patients with 230 critically ischemic limbs, treated with consecutive percutaneous transluminal angioplasty (PTA) at Helsinki University Central Hospital between January 2000 and December 2002 were collected and analyzed retrospectively. Patency, limb salvage, and survival rates were calculated on an intention‐to‐treat basis. Comparisons were done with univariate (Kaplan‐Meier) and multivariate analysis (Cox regression).

Results: Overall primary patency, secondary patency, limb salvage, and survival rates were 47%, 59%, 92%, and 76%, respectively, at 12 months. In the multivariate analysis, low toe pressure (⩽30 mmHg) was a significant risk factor for poor patency. Uremia with hemodialysis, low toe pressure (⩽30 mmHg), and hemodynamic failure of the endovascular procedure were found to increase significantly the risk of amputation. Uremia with hemodialysis, coronary artery disease, tissue loss as indication for PTA (Fontaine stage IV), and age over 70 years were all found to increase significantly the risk of death.

Conclusion: Infra‐inguinal PTA is feasible in patients with CLI and resulted in good limb salvage.
Diagnostic performance of computed tomography colonography and colonoscopy: a prospective and validated analysis of 231 paired examinations
Authors: Arnesen R. B. , von Benzon E. , Adamsen S. , Svendsen L. B. , Raaschou H. O. , Hart Hansen O.
Published: December 2009

Background: Detection of colorectal tumors with computed tomography colonography (CTC) is an alternative to conventional colonoscopy (CC), and clarification of the diagnostic performance is essential for cost-effective use of both technologies.

Purpose: To evaluate the diagnostic performance of CTC compared with CC.

Material and Methods: 231 consecutive CTCs were performed prior to same-day scheduled CC. The radiologist and endoscopists were blinded to each other's findings. Patients underwent a polyethylene glycol bowel preparation, and were scanned in prone and supine positions using a single-detector helical CT scanner and commercially available software for image analysis. Findings were validated (matched) in an unblinded comparison with video-recordings of the CCs and re-CCs in cases of doubt.

Results: For patients with polyps ⩾5 mm and ⩾10 mm, the sensitivity was 69% (95% CI 58–80%) and 81% (68–94%), and the specificity was 91% (84–98%) and 98% (93–100%), respectively. For detection of polyps ⩾5 mm and ⩾10 mm, the sensitivity was 66% (57–75%) and 77% (65–89%). A flat, elevated low-grade carcinoma was missed by CTC. One cancer relapse was missed by CC, and a cecal cancer was missed by an incomplete CC and follow-up double-contrast barium enema.

Conclusion: CC was superior to CTC and should remain first choice for the diagnosis of colorectal polyps. However, for diagnosis of lesions ⩾10 mm, CTC and CC should be considered as complementary methods.
Teleradiology uppsala–sydney for nighttime emergencies: preliminary experience
Authors: Eklöf H. , Radecka E. , Liss P.
Published: December 2009

Background: The development of digital imaging systems for radiology in combination with the possibility to transfer large quantities of data over the Internet has increased the interest in teleradiology. Transferring nighttime examinations to an evaluation center in a daytime zone may provide improved patient security, better working hours for radiologists, and reduced costs for emergency radiological services.

Purpose: To evaluate the time required for transferring radiological information from Uppsala (Sweden) to Sydney (Australia).

Material and Methods: A radiologist in Sydney reported on radiological examinations performed in Uppsala. The time required for downloading 75 examinations and returning 24 reports was registered.

Results: Downloading was completed in <60 min for all conventional radiological examinations, but only 44% of computed tomography (CT) examinations with >65 images. Reports were completed in <10 min. Turnaround time was directly related to the time required for downloading the images. The Sydney report was available in Uppsala within 30 min of the in-house report in 79% of examinations.

Conclusion: The main challenge for emergency teleradiology is the time required for downloading large volumes of data over the Internet.
Computed tomography manifestations of renal hemangiopericytoma
Authors: Hayasaka K. , Nihashi T. , Nojiri Y. , Okamuara K.
Published: December 2009

Renal hemangiopericytoma (HPC) is a rare tumor. There are no unique radiological findings that can reliably aid in its preoperative diagnosis. A 60-year-old Japanese male was admitted for an abdominal mass. Ultrasound revealed a heterogeneous hyperechoic mass. Computed tomography (CT) showed a heterogeneous mass and tumor vascularity by a precontrast and dynamic study with maximum intensity projection (MIP) and volume-rendering technique (VRT). Radical nephrectomy was performed, and the histopathogic diagnosis revealed renal HPC.
Breast MRI in the evaluation of locally recurrent or new breast cancer in the postoperative patient: correlation of morphology and enhancement features with the BI-RADS category
Authors: Seely J. M. , Nguyen E. T. , Jaffey J.
Published: December 2009

Background: While breast magnetic resonance imaging (MRI) is a highly sensitive test for detecting breast carcinoma, its specificity is lower, and several methods have been described on how to optimize specificity.

Purpose: To compare the specificity and sensitivity of the BI-RADS category with the Fischer score in breast MRI for diagnosing cancer in women previously treated for breast cancer.

Material and Methods: Women referred for evaluation of possible local recurrence or new breast cancer underwent breast MRI examination. Morphologic and kinetic enhancement characteristics were evaluated. BI-RADS category and Fischer score were assigned for each enhancing lesion and compared using a chi-square test. Sensitivity, specificity, and positive predictive values for 27 morphologic and enhancement characteristics were calculated. Pathologic diagnosis was obtained in all patients with enhancing lesions who had ultrasound or mammographic correlation. In those without correlate, 6-, 12-, and 24-month follow-up breast MRIs were obtained. Interobserver kappa correlation was determined for each variable studied.

Results: 34 benign and 32 malignant lesions were identified in 26 of 30 patients. BI-RADS category yielded a specificity of 77.1% and a sensitivity of 81.8%. Fischer score had a lower specificity and sensitivity (62.9% and 72.7%, respectively) ( P<0.0001). Of the 27 variables studied, >100% enhancement was more sensitive than BI-RADS for malignant lesions. Specificity was highest for rim enhancement (97.1%), but sensitivity was low (24.2%). Interobserver kappa correlation was good for all 27 characteristics (κ = 0.84), and highest for BI-RADS assessment (κ = 0.91).

Conclusion: BI-RADS category in breast MRI had the highest combination of specificity and sensitivity, and the highest interobserver correlation. Fischer score and other morphologic and enhancement features lack sensitivity or specificity and do not have high positive predictive values when analyzed as single independent variables.
Assessment of local control after laser-induced thermotherapy of liver metastases from colorectal cancer: contribution of FDG-PET in patients with clinical suspicion of progressive disease
Authors: Denecke T. , Steffen I. , Hildebrandt B. , Rühl R. , Streitparth F. , Lehmkuhl L. , Langrehr J. , Ricke J. , Amthauer H. , Lopez Hänninen E.
Published: December 2009

Background: Management of patients after locally ablative treatment of liver metastases requires exact information about local control and systemic disease status. To fulfill these requirements, whole-body imaging using positron emission tomography with 18F-fluorodeoxyglucose (FDG-PET) is a promising alternative to morphologic imaging modalities such as computed tomography (CT) and magnetic resonance imaging (MRI).

Purpose: To evaluate FDG-PET for the assessment of local control and systemic disease in patients with clinical suspicion of tumor progression after laser-induced thermotherapy (LITT) of colorectal liver metastases.

Material and Methods: In 21 patients with suspicion of progressive disease after LITT, whole-body FDG-PET was performed. The presence of viable tumor within treated lesions, new liver metastases, and extrahepatic disease was evaluated visually and semiquantitatively (maximal standard uptake value [SUVmax], tumor-to-normal ratio [T/N]). The standard of reference was histopathology ( n = 25 lesions) and/or clinical follow-up (>12 months) including contrast-enhanced MRI of the liver.

Results: Among 54 metastases treated with LITT, 29 had residual tumor. Receiver operating characteristic (ROC) analysis of SUVmax (area under the curve (AUC) 0.990) and T/N (AUC 0.968) showed a significant discrimination level of negative or positive lesion status with an equal accuracy of 94% (51/54). The overall accuracy of visual FDG-PET was 96% (52/54), with one false-negative lesion among six examined within 3 days after LITT, and one false-positive lesion examined 54 days after LITT. In the detection of new intra- and extrahepatic lesions, FDG-PET resulted in correct alteration of treatment strategy in 43% of patients ( P = 0.007).

Conclusion: FDG-PET is a promising tool for the assessment of local control and whole-body restaging in patients with clinical suspicion of tumor progression after locally ablative treatment of colorectal liver metastases with LITT.
Twitter Triumphs
Authors: van der Zee Bibi
Published: December 2009

It has been the year of the tweet, as protesters and activists embrace technology in the name of political change. Bibi van der Zee assesses the impact
Iran Uncut
Authors: Halasa Malu
Published: December 2009

Malu Halasa explains why the Iranian authorities want to censor images as much as words
See No Evil
Authors: Klausen Jytte
Published: December 2009

Jytte Klausen talks to Index about her new book on the Danish cartoons crisis and discusses why it was published without any illustrations
Years of Living Dangerously
Authors: Maryniak Irena
Published: December 2009

Maria Eismont talks to Dmitry Muratov, editor of the newspaper Novaya Gazeta, about his struggle for press freedom and justice in Russia
Book Reviews
Authors: Rossitti Sandro , Bjerner Tomas , Wegenius Göran , Nilsson Sven
Published: December 2009

Imaging of Brain Tumors with Histological Correlations. Edited by A. Drevelegas. Springer-Verlag 2002. ISBN 3-540-41092-9. X+302 pages, 309 figures. Price hardback: €129.00.

Anatomy in Diagnostic Imaging, 2nd edn. By P. Fleckenstein and J. Tranum-Jensen. Munksgaard 2001. ISBN 87-16-12336-0.

The Imaging of Tuberculosis. With Epidemiological, Pathological, and Clinical Correlation. By P. E. S. Palmer. Springer-Verlag 2002. ISBN 3-540-41821-0. Price hardcover: €49.95+VAT.

Radiological Imaging of the Small Intestine. Edited by N. C. Gourtsoyiannis. Springer-Verlag 2002. ISBN 3-540- 65520-4. Price: Hardcover € 214.

Osteoporosis: Pathophysiology and Clinical Management. Edited by E. S. Orwell and M. Bliziotes. Humana Press 2003. ISBN 0-89603-933-1. Price: USD 135.
A modified sonographic technique for assessment of gastric emptying of liquid
Authors: Pedersen J. F.
Published: December 2009

Purpose: Ultrasound scanning is replacing scintigraphy in studies of gastric emptying of liquid, but both have considerable day-to-day variability. This study describes a modified ultrasound technique for assessing gastric emptying of liquid, and evaluates the inter- and intraindividual variation in emptying time.

Material and Methods: On different days, each of 12 healthy volunteers had meals of 350 ml broth. The antral area was measured at sonography 5 times before the meal as a baseline, and every 1–4 min after the meal. The time until the antral area had decreased to 150% of baseline (T150) was determined and used as surrogate expression of gastric emptying time.

Results: The mean T150 for a broth meal was 12.6 min (range 5–21) and 13.5 min (6–23) (first and second meal, respectively). The standard deviation of the differences between the 12 pairs of repeated measurements was 3.1 min and the coefficient of variation was 24%.

Conclusion: Ultrasound monitoring of antral size after a liquid meal is a well suited method for assessing gastric emptying of liquid.
Elective placement of covered stents in native coronary arteries
Authors: Søvik E. , Kløw N-E. , Brekke M. , Stavnes S.
Published: December 2009

Purpose: To study the feasibility of placing a polytetrafluoroethylene (PTFE)-covered stent graft into native coronary arteries and assess the complications and the restenosis rate.

Material and Methods: Fifty consecutive patients with stable angina pectoris were included and the stent graft was placed into native coronary arteries. Clinical and angiographic follow-up were performed after 6 months.

Results: The stent grafts were successfully placed in all patients. The mean reference diameter was 3.3 ± 0.6 mm. During follow-up the stent grafts occluded in patients after 1, 2 and 2.5 months and one more was occluded at 6 months. Three patients experienced myocardial infarction, 2 Q wave and one non-Q wave. After 6 months 42 (84%) patients had angina NYHA class 0 or 1. Target vessel revascularization was done in 11 cases for restenosis in the graft (n = 4), outside the graft (n = 3) and both (n = 4), giving a restenosis rate of 24%. The total major adverse coronary events at 6 months was 24%.

Conclusion: The stent graft was deployed with a high success rate. The restenosis rate was not higher than expected for bare stents. However, this study showed that subacute occlusion may occur more frequently and we therefore recommend that ticlopidine or clopidogrel treatment should be prolonged to at least 3 months.
Morphologic and histopathologic changes in the bowel after super-selective transcatheter embolization for focal lower gastrointestinal hemorrhage
Authors: Horiguchi J. , Naito A. , Fukuda H. , Nakashige A. , Ito K. , Kiso T. , Mori M.
Published: December 2009

Purpose: To evaluate the safety of superselective arterial embolization therapy in the lower gastrointestinal tract. The sequelae on normal enteric tissue in lower gastrointestinal arterial embolization were retrospectively reviewed.

Material and Methods: To control hemorrhage and tumor blood supply, 14 patients were treated by superselective transcatheter embolization at different levels of the colonic and small intestine vessels via the superior and inferior mesenteric arteries using microcoils and/or gelatin sponge. Normal enteric tissues in the embolized areas were analyzed for the occurrence of ischemic changes by clinical follow-up, colonoscopy, and surgery.

Results: Normal bowel function was preserved in 13 patients. In 1 patient treated with numerous gelatin sponge particles delivered from the proximal arcade of the superior mesenteric artery, significant muscular fibrosis occurred.

Conclusion: Superselective arterial embolization for lower gastrointestinal hemorrhage can be safely performed by minimizing the amount of embolic materials and delivering them as distally as possible.
Imaging of esophageal tuberculosis: A review of 23 cases
Authors: Nagi B. , Lal A. , Kochhar R. , Bhasin D. K. , Gulati M. , Suri S. , Singh K.
Published: December 2009

Purpose: To evaluate the various radiological abnormalities in patients with proven esophageal tuberculosis.

Material and Methods: The case records of 23 patients with proven esophageal tuberculosis were evaluated retrospectively for various radiological abnormalities. Twenty-two patients had secondary involvement of esophagus in the form of direct extension of mediastinal and pulmonary tuberculosis or spinal tuberculosis. Only 1 patient had primary involvement of the esophagus with no evidence of disease elsewhere. The diagnosis was confirmed by endoscopic and CT-guided biopsy/aspiration cytology in 7 and 6 cases, respectively. Diagnosis was made on the basis of surgical biopsy of lymph node and autopsy in 1 patient each. In the remaining 8 patients the diagnosis was based on radiological and endoscopic findings and the response to antituberculous treatment.

Results: Chest radiography (CXR) was abnormal in 65% patients. While the findings were non-conclusive for esophageal tuberculosis, characteristic lesions of tuberculosis in lungs or spine were suggestive of tuberculous etiology. In 15 patients, CT of the chest confirmed the corresponding CXR findings and also showed additional findings of mediastinal lymphadenopathy when CXR was normal. Fourteen patients showed mediastinal lymphadenopathy on CT of the chest. In all these patients, more than one group of lymph nodes was involved. The characteristic hypodense center of lymph nodes suggestive of tuberculosis was seen in 12 patients. Radiological abnormalities seen in barium swallow examination were extrinsic compression, traction diverticula, strictures, sinus/fistulous tracts, kinking and pseudotumor mass of esophagus in decreasing order of frequency. The middle third of the esophagus was found to be the most frequent site of involvement.
Altered response in renal blood flow and oxygen tension to contrast media in diabetic rats
Authors: Palm F. , Carlsson P.-O. , Hansell P. , Hellberg O. , Nygren A. , Liss P.
Published: December 2009

Purpose: To investigate the effect of the contrast medium (CM) iopromide on renal microcirculation and oxygen tension in non-diabetic control and streptozotocin-diabetic Wistar Furth rats.

Materials and Methods: Oxygen tension was measured with Clark-type microelectrodes and blood flow with laser-Doppler flow probes. In order to differentiate between an acutely increased blood glucose concentration and a long-term diabetic state, some of the non-diabetic control rats were intravenously infused with glucose.

Results: CM decreased the medullary oxygen tension in control (non-diabetic normoglycemic) rats (∼35%) but not in diabetic rats. Medullary blood flow in control rats increased after CM administration and remained elevated, while it was unchanged in the diabetic rats. In response to CM, glucose-infused control rats responded similarly to control animals in medullary oxygen tension, but similarly to diabetic rats in medullary blood flow. Contrary to in control rats, medullary oxygen tension was unchanged in diabetic animals after CM administration.

Conclusion: Streptozotocin-diabetic rats have an altered response to intravenous injection of the CM iopromide compared to non-diabetic rats. The unaltered medullary oxygen tension, seen in the diabetic group after injection of CM, suggests that non-hemodynamic mechanisms are responsible for the increased frequency of renal failure commonly seen among diabetic patients.