bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling the effects of eruptive and seismic activities on flank instability at Mount Etna, Italy
Authors: Bozzano F. , Gaeta M. , Lenti L. , Martino S. , Paciello A. , Palladino D. M. , Sottili G.
Published: October 2013

The identification and evaluation of trigger mechanisms for volcano flank instabilities and/or collapse represent a key issue for risk assessment in densely populated volcanic areas, as well as in long‐distance settings, particularly in case of island or coastal volcanoes. Here we address quantitatively the effects of external (seismic) and inner (magmatic) forcing on the stress‐strain state associated to flank instabilities at Mount Etna (Sicily, southern Italy) by means of a 2‐D finite difference method numerical modeling. Modeled seismic actions include strong near‐field, strong far‐field, and low‐magnitude near‐field earthquakes. Magmatic actions consider the inner pressure changes induced by energetic lava fountains in the summit crater area and subvertical and oblique dike ascent below the summit area. Model results are validated in light of available monitoring data and recent eruptive activity. Numerical results show that the main strain effects are produced by high‐magnitude near‐field earthquakes (expected return time of ~103yrs) and by vertical uprise of a magma dike below the volcano summit area. Maximum displacements in the order of tens of centimeters may involve the summit area, up to some 106m3/m over some kilometers laterally. Stress releases up to 107Pa may affect a limited portion of the magmatic conduit, thus favoring major effusive flank eruptions. Major catastrophic events, such as volcano flank collapse, should not be expected by applying, either individually or combined, the aforementioned actions.
Active accommodation of plate convergence in Southern Iran: Earthquake locations, triggered aseismic slip, and regional strain rates
Authors: Barnhart William D. , Lohman Rowena B. , Mellors Robert J.
Published: October 2013

We present a catalog of interferometric synthetic aperture radar (InSAR) constraints on deformation that occurred during earthquake sequences in southern Iran between 1992 and 2011, and explore the implications on the accommodation of large‐scale continental convergence between Saudi Arabia and Eurasia within the Zagros Mountains. The Zagros Mountains, a salt‐laden fold‐and‐thrust belt involving ~10 km of sedimentary rocks overlying Precambrian basement rocks, have formed as a result of ongoing continental collision since 10–20 Ma that is currently occurring at a rate of ~3 cm/yr. We first demonstrate that there is a biased misfit in earthquake locations in global catalogs that likely results from neglect of 3‐D velocity structure. Previous work involving two M ~ 6 earthquakes with well‐recorded aftershocks has shown that the deformation observed with InSAR may represent triggered slip on faults much shallower than the primary earthquake, which likely occurred within the basement rocks (>10 km depth). We explore the hypothesis that most of the deformation observed with InSAR spanning earthquake sequences is also due to shallow, triggered slip above a deeper earthquake, effectively doubling the moment release for each event. We quantify the effects that this extra moment release would have on the discrepancy between seismically and geodetically constrained moment rates in the region, finding that even with the extra triggered fault slip, significant aseismic deformation during the interseismic period is necessary to fully explain the convergence between Eurasia and Saudi Arabia.
Deep‐sea magnetic vector anomalies over the Hakurei hydrothermal field and the Bayonnaise knoll caldera, Izu‐Ogasawara arc, Japan
Authors: Honsho Chie , Ura Tamaki , Kim Kangsoo
Published: October 2013

We conducted deep‐sea magnetic measurements using autonomous underwater vehicles in the Bayonnaise knoll caldera, the Izu‐Ogasawara island arc, which hosts the large Hakurei hydrothermal field. We improved the conventional correction method applied for removing the effect of vehicle magnetization, thus greatly enhancing the precision of the resulting vector anomalies. The magnetization distribution obtained from the vector anomaly data shows a ∼2 km wide belt of high magnetization, trending NNW‐SSE going through the caldera, and a low‐magnetization zone ∼300 m by ∼500 m in area, extending over the Hakurei site. Comparison between the results obtained using the vector anomaly and the total intensity anomaly shows that the magnetic field is determined more accurately, especially in areas of sparse data distribution, when the vector anomaly rather than the total intensity anomaly is used. We suggest a geologically motivated model that basaltic volcanism associated with the back‐arc rifting occurred after the formation of the caldera, resulting in the formation of the high‐magnetization belt underneath the silicic caldera. The Hakurei hydrothermal field lies in the intersection of the basaltic volcanism belt and the caldera wall fault, suggesting a mechanism that hot water generated by the heat of the volcanic activity has been spouting out through the caldera wall fault. The deposit apparently extends beyond the low‐magnetization zone, climbing up the caldera wall. This may indicate that hot water rising from the deep through the alteration zone is transported laterally when it comes near the seafloor along fissures and fractures in the caldera wall.
Seismic shear wave reflectivity structure of the mantle beneath northeast China and the northwest Pacific
Authors: Bagley Brian , Courtier Anna M. , Revenaugh Justin
Published: October 2013

Using multiple ScS reverberations, we examine the mantle reflectivity structure beneath northeast China and the northwest Pacific. We find several upper mantle discontinuities, including a melt layer with a mean thickness of 64 km atop the 410 km discontinuity, present on both sides of the subducting slab near the Nankai trench. The transition zone contains a split 520 km discontinuity in several paths, and tomographic images show stagnant slabs at this depth. We believe that this may be slab related based on experimental work. A negative reflector is found in one path beneath the northeast China craton at a depth of 598 km. Mid‐mantle reflectors are found in all of our paths and are present throughout a wide depth range (~750–1600 km).
Testing atmospheric and tidal earthquake triggering at Mt. Hochstaufen, Germany
Authors: Hainzl S. , Ben‐Zion Y. , Cattania C. , Wassermann J.
Published: October 2013

Seismicity closely related to hydrological impacts has been observed in several locations worldwide, particularly in intraplate areas where tectonic stressing rates are small. The triggering mechanism is usually explained by a poroelastic response of the seismogenic crust to surface water flux, leading to pore pressure changes at depth. To explain the earthquake triggering in response of those small stress changes, however, the crust has to be near a critical state in which other transient processes might be significant. One of the prominent examples is at Mt. Hochstaufen in SE Germany, where seismicity is known to vary seasonally. A previous analysis showed that the seismicity in 2002 was highly correlated with model forecasts based on fluid diffusion and rate‐ and state‐dependent frictional nucleation. Here we revisit this case by accounting additionally for poroelastic effects, as well as for thermoelastic and tidal stresses. We also test whether the model can explain the observations of the subsequent 8 years between 2003 and 2010. Our analysis confirms that rainfall is the dominant driving force in this region. The model not only fits the year 2002 activity very well but also provides with the same parameters a reasonable fit to the subsequent period, with a probability gain of about 4 per event in comparison to a time‐independent Poisson model.
Inversion for absolute deviatoric crustal stress using focal mechanisms and coseismic stress changes: The 2011 M9 Tohoku‐oki, Japan, earthquake
Authors: Yang Yi‐Rong , Johnson Kaj M. , Chuang Ray Y.
Published: October 2013

The absolute magnitude of stress in the crust and the shear strength of faults are poorly known, yet fundamental quantities, in lithospheric dynamics. While stress magnitude cannot be measured directly, deviatoric stress state can be inferred indirectly from focal mechanism solutions collected before and after an earthquake. We extend a standard stress inversion for normalized stresses to invert for the 3‐D spatial distribution of absolute deviatoric stress and variation of fault strength with depth using focal mechanism solutions and coseismic stress changes produced by large earthquakes. We apply the method to the 2011 M9 Tohoku‐oki, Japan, earthquake. The northern Japan fore‐arc crust between 5 and 15 km depths appears to be weak with fault strength of 40–90 MPa, consistent with a coefficient of friction of 0.2–0.5. The M9 Tohoku‐oki coseismic stress change was large enough, relative to the ambient stress, to rotate the principal stress directions typically ~20° in the upper 20 km of the crust. The data from Japan require a heterogeneous ambient deviatoric stress field with short‐wavelength (~20–50 km) fluctuations in principal stress orientations.
GlobalPwave tomography of Earth's lowermost mantle from partition modeling
Authors: Young M. K. , Tkalc̆ić H. , Bodin T. , Sambridge M.
Published: October 2013

Determining the scale‐length, magnitude, and distribution of heterogeneity in the lowermost mantle is crucial to understanding whole mantle dynamics, and yet it remains a much debated and ongoing challenge in geophysics. Common shortcomings of current seismically derived lowermost mantle models are incomplete raypath coverage, arbitrary model parameterization, inaccurate uncertainty estimates, and an ad hoc definition of the misfit function in the optimization framework. In response, we present a new approach to global tomography. Apart from improving the existing raypath coverage using only high‐quality cross‐correlated waveforms, the problem is addressed within a Bayesian framework where explicit regularization of model parameters is not required. We obtain high‐resolution images, complete with uncertainty estimates, of the lowermost mantlePwave velocity structure using a hand‐picked data set ofPKPab‐df,PKPbc‐df, andPcP‐Pdifferential travel times. Most importantly, our results demonstrate that the root mean square of thePwave velocity variations in the lowermost mantle is approximately 0.87%, which is 3 times larger than previous global‐scale estimates.
Feedbacks in a coupled ice‐atmosphere‐dust model of the glacial Neoproterozoic “Mudball Earth”
Authors: Goodman Jason C. , Strom Dana C.
Published: October 2013

The climate state of an ice‐covered Neoproterozoic “Snowball Earth” climate is highly sensitive to the presence of dust on the ice. Other authors have noted that the accumulation of dust can lower the albedo of an ice‐covered world enough to allow deglaciation even with fairly modest amounts of greenhouse gas warming. Here, we model the accumulation, transport, and removal of dust in a coupled ice‐atmosphere‐dust climate model, operating within the simplified framework of a one‐dimensional energy balance climate model. We confirm that the buildup of low‐albedo dust makes our model easier to deglaciate (requiring orders of magnitude less carbon dioxide than a no‐dust model) and discover novel climate feedbacks and chaos in the dusty ice system. As dust accumulates, its low albedo warms the ice and can cause it to melt: in our model, the meltwater carries away dust, leading to both a simple negative feedback (the “dust thermostat”) and chaotic oscillations. The feedback is robust over a broad range of model parameters, but the chaotic oscillations are sensitive to model resolution.
Suomi NPP VIIRS prelaunch and on‐orbit geometric calibration and characterization
Authors: Wolfe Robert E. , Lin Guoqing , Nishihama Masahiro , Tewari Krishna P. , Tilton James C. , Isaacman Alice R.
Published: October 2013

The Visible Infrared Imaging Radiometer Suite (VIIRS) sensor was launched 28 October 2011 on the Suomi National Polar‐orbiting Partnership (SNPP) satellite. VIIRS has 22 spectral bands covering the spectrum between 0.412 µm and 12.01 µm, including 16 moderate resolution bands (M‐bands) with a nominal spatial resolution of 750 m at nadir, five imaging resolution bands (I‐bands) with a nominal spatial resolution of 375 m at nadir, and a day‐night band (DNB) with a near‐constant nominal 750 m spatial resolution throughout the scan. These bands are located in a visible and near‐infrared focal plane assembly (FPA), a shortwave and midwave infrared FPA, and a long‐wave infrared FPA. All bands, except the DNB, are coregistered for proper environmental data records retrievals. Observations from VIIRS instrument provide long‐term measurements of biogeophysical variables for climate research and polar satellite data stream for the operational community's use in weather forecasting and disaster relief and other applications. Well Earth‐located (geolocated) instrument data are important to retrieving accurate biogeophysical variables. This paper describes prelaunch pointing and alignment measurements, and the two sets of on‐orbit correction of geolocation errors, the first of which corrected error from 1300 m to within 75 m (20% I‐band pixel size) and the second of which fine‐tuned scan‐angle dependent errors, bringing VIIRS geolocation products to high maturity in one and a half years of the SNPP VIIRS on‐orbit operations. Prelaunch calibration and the on‐orbit characterization of sensor spatial impulse responses and band‐to‐band coregistration are also described.
Surface mass balance on Fimbul ice shelf, East Antarctica: Comparison of field measurements and large‐scale studies
Authors: Sinisalo Anna , Anschütz Helgard , Aasen Anne Tårånd , Langley Kirsty , von Deschwanden Angela , Kohler Jack , Matsuoka Kenichi , Hamran Svein‐ Erik , Øyan Mats‐Jørgen , Schlosser Elisabeth , Hagen Jon Ove , Nøst Ole Anders , Isaksson Elisabeth
Published: October 2013

Many challenges remain for estimating the Antarctic ice sheet surface mass balance (SMB), which represents a major uncertainty in predictions of future sea‐level rise. Validating continental scale studies is hampered by the sparse distribution of in situ data. Here we present a 26 year mean SMB of the Fimbul ice shelf in East Antarctica between 1983–2009, and recent interannual variability since 2010. We compare these data to the results of large‐scale SMB studies for similar time periods, obtained from regional atmospheric modeling and remote sensing. Our in situ data include ground penetrating radar, firn cores, and mass balance stakes and provide information on both temporal and spatial scales. The 26 year mean SMB on the Fimbul ice shelf varies between 170 and 620 kg m−2 a−1 giving a regional average value of 310 ± 70 kg m−2 a−1. Our measurements indicate higher long‐term accumulation over large parts of the ice shelf compared to the large‐scale studies. We also show that the variability of the mean annual SMB, which can be up to 90%, can be a dominant factor in short‐term estimates. The results emphasize the importance of using a combination of ground‐based validation data, regional climate models, and remote sensing over a relevant time period in order to achieve a reliable SMB for Antarctica.
New nitric oxide (NO) nightglow measurements with SPICAM/MEx as a tracer of Mars upper atmosphere circulation and comparison with LMD‐MGCM model prediction: Evidence for asymmetric hemispheres
Authors: Gagné Marie‐Ève , Bertaux Jean‐Loup , González‐Galindo Francisco , Melo Stella M. L. , Montmessin Franck , Strong Kimberly
Published: October 2013

We report observations of NO nightglow with the Spectroscopy for the Investigation of the Characteristics of the Atmosphere of Mars (SPICAM) experiment on board the Mars Express (MEx) spacecraft. NO molecules emit an ultraviolet photon when N and O atoms (produced at high altitude in the thermosphere) recombine. Therefore, this emission is a tracer of the atmospheric dynamics in the lower thermosphere where O and N atoms are produced, and below, in the altitude region 50–100 km where the emission is detected. A new retrieval method has been developed to analyze the measurements from this instrument in the stellar occultation mode without slit and retrieve the absolute brightness of the emission. We present the results from the processing of more than 2000 orbits, providing the first global latitude‐season distribution of the emission, established over three Martian years. The results are globally consistent with previously available measurements of dedicated limb nightglow obtained during the first Martian year of MEx (MY27). We compared the ensemble of both data sets with the predictions of the Laboratoire de Météorologie Dynamique Mars General Circulation Model (LMD‐MGCM), with the addition of the full chemistry of N atoms. We find an overall agreement between the observed and modeled airglow intensities, but discrepancies are also found. The frequency and magnitude of the NO airglow observations show important asymmetries between the Northern and the Southern Hemispheres. There is no detection of emission near the poles during equinox conditions, while the model predicts that it should be most intense because of a circulation with two descending branches at the poles.
The evolving application of single‐port robotic surgery in general surgery
Authors: Qadan Motaz , Curet Myriam J. , Wren Sherry M.
Published: October 2013

Advances in the field of minimally invasive surgery have grown since the original advent of conventional multiport laparoscopic surgery. The recent development of single incision laparoscopic surgery remains a relatively novel technique, and has had mixed reviews as to whether it has been associated with lower pain scores, shorter hospital stays, and higher satisfaction levels among patients undergoing procedures through cosmetically‐appeasing single incisions. However, due to technical difficulties that arise from the clustering of laparoscopic instruments through a confined working space, such as loss of instrument triangulation, poor surgical exposure, and instrument clashing, uptake by surgeons without a specific interest and expertise in cutting‐edge minimally invasive approaches has been limited. The parallel use of robotic surgery with single‐port platforms, however, appears to counteract technical issues associated with single incision laparoscopic surgery through significant ergonomic improvements, including enhanced instrument triangulation, organ retraction, and camera localization within the surgical field. By combining the use of the robot with the single incision platform, the recognized challenges of single incision laparoscopic surgery are simplified, while maintaining potential advantages of the single‐incision minimally invasive approach. This review provides a comprehensive report of the evolving application single‐port robotic surgery in the field of general surgery today.
Guanidinum Chloride as Dehydrocyclization Agent in the Synthesis of 2‐Fuctionalized (4H)‐3,1‐Benzoxazine‐4‐ones
Authors: Nikpour Farzad , Bahmani Asrin , Havasi Forugh , Sharafi‐Kolkeshvandi Mahnaz
Published: October 2013

A facile and expedient route for the synthesis of 2‐ethoxy‐ and 2‐(ethylcarboxylate)‐(4H)‐3,1‐benzoxazine‐4‐ones is described using guanidinium chloride as a safe and convenient dehydrocyclization agent. High yields of the products obtain under mild reaction conditions without need to use of any catalyst and with easy work‐up of the reaction mixture.
Do internal medicine interns practice etiquette‐based communication? A critical look at the inpatient encounter
Authors: Block Lauren , Hutzler Lindsey , Habicht Robert , Wu Albert W. , Desai Sanjay V. , Novello Silva Kathryn , Niessen Timothy , Oliver Nora , Feldman Leonard
Published: October 2013

Etiquette‐based communication may improve the inpatient experience but is not universally practiced. We sought to determine the extent to which internal medicine interns practice behaviors that characterize etiquette‐based medicine. Trained observers evaluated the use of 5 key communication strategies by internal medicine interns during inpatient clinical encounters: introducing one's self, explaining one's role in the patient's care, touching the patient, asking open‐ended questions, and sitting down with the patient. Participants at 1 site then completed a survey estimating how frequently they performed each of the observed behaviors. A convenience sample of 29 interns was observed on a total of 732 patient encounters. Overall, interns introduced themselves 40% of the time and explained their role 37% of the time. Interns touched patients on 65% of visits, asked open‐ended questions on 75% of visits, and sat down with patients during 9% of visits. Interns at 1 site estimated introducing themselves and their role and sitting with patients significantly more frequently than was observed (80% vs 40%, P < 0.01; 80% vs 37%, P < 0.01; and 58% vs 9%, P < 0.01, respectively). Resident physicians introduced themselves to patients, explained their role, and sat down with patients infrequently during observed inpatient encounters. Residents surveyed tended to overestimate their own practice of etiquette‐based medicine. Journal of Hospital Medicine 2013;8:631–634. © 2013 Society of Hospital Medicine
A convergent stereocontrolled synthesis of [3‐14C]solanesol
Authors: Roe Stephen J. , Oldfield Mark F. , Geach Neil , Baxter Andrew
Published: October 2013

In this communication, we report the synthesis of ~5 mCi of [3‐14C]solanesol (1) prepared from ethyl [3‐14C]acetoacetate and (all‐E)‐octaprenyl bromide (2) in four steps, with a specific radioactivity of 19.83 mCi/mmol and with a chemical/stereochemical and radiochemical purity of ≥ 95%. (Figure ). Position 3 of the chain was selected for 14C labelling because of the metabolic stability of this position. Unlabelled (all‐E)‐octaprenyl (18) (Scheme ) necessary for this work was prepared via a convergent iterative ‘allyl‐allyl’ coupling approach of precursors easily derived from readily available inexpensive starting materials.1 Copyright © 2013 John Wiley & Sons, Ltd.
Evaluation of the efficiency of Pd/H2‐catalyzed benzylic H/D exchange of dehydroabietinal with D2O and synthesis of a tritium‐labeled analogue
Authors: Petros Robby A. , Shah Jyoti
Published: October 2013

Dehydroabietinal (DA) has been identified as an important signaling molecule in systemic acquired resistance in plants. Deuterium and tritium‐labeled DA were synthesized to confirm its role in signaling and to further elucidate the mechanism by which DA induces systemic acquired resistance. Pd/H2‐catalyzed exchange of benzylic hydrogen atoms of DA with 2H‐H2O or 3H‐H2O was conducted with >97% label incorporation for 2H‐DA and a specific activity of 12.6 mCi/mmol for 3H‐DA synthesized from 90 mCi/mmol 3H‐H2O. The extent of deuterium labeling at each benzylic position was determined via an inverse‐gated 13C NMR experiment. C7 and C15 were 87% and 81% labeled, respectively. Isotope‐induced chemical shift changes at C6 were used to approximate the amount of singly (66%) and doubly (17%) labeled 2H‐DA at C7. Results also indicated that two of the three benzylic protons in DA underwent facile exchange. Exchange at the remaining position was likely hampered by steric interactions of nearby methyl groups at the surface of the Pd catalyst.
Development of the trigeminal motor neurons in parrots: Implications for the role of nervous tissue in the evolution of jaw muscle morphology
Authors: Tokita Masayoshi , Nakayama Tomoki
Published: October 2013

Vertebrates have succeeded to inhabit almost every ecological niche due in large part to the anatomical diversification of their jaw complex. As a component of the feeding apparatus, jaw muscles carry a vital role for determining the mode of feeding. Early patterning of the jaw muscles has been attributed to cranial neural crest‐derived mesenchyme, however, much remains to be understood about the role of nonneural crest tissues in the evolution and diversification of jaw muscle morphology. In this study, we describe the development of trigeminal motor neurons in a parrot species with the uniquely shaped jaw muscles and compare its developmental pattern to that in the quail with the standard jaw muscles to uncover potential roles of nervous tissue in the evolution of vertebrate jaw muscles. In parrot embryogenesis, the motor axon bundles are detectable within the muscular tissue only after the basic shape of the muscular tissue has been established. This supports the view that nervous tissue does not primarily determine the spatial pattern of jaw muscles. In contrast, the trigeminal motor nucleus, which is composed of somata of neurons that innervate major jaw muscles, of parrot is more developed compared to quail, even in embryonic stage where no remarkable interspecific difference in both jaw muscle morphology and motor nerve branching pattern is recognized. Our data suggest that although nervous tissue may not have a large influence on initial patterning of jaw muscles, it may play an important role in subsequent growth and maintenance of muscular tissue and alterations in cranial nervous tissue development may underlie diversification of jaw muscle morphology. J. Morphol. 275:191–205, 2014. © 2013 Wiley Periodicals, Inc.
Lung injury induced by secondhand smoke exposure detected with hyperpolarized helium‐3 diffusion MR
Authors: Wang Chengbo , Mugler John P. , de Lange Eduard E. , Patrie James T. , Mata Jaime F. , Altes Talissa A.
Published: October 2013

Purpose

To determine whether helium‐3 diffusion MR can detect the changes in the lungs of healthy nonsmoking individuals who were regularly exposed to secondhand smoke.

Materials and Methods

Three groups were studied (age: 59 ± 9 years): 23 smokers, 37 exposure‐to‐secondhand‐smoke subjects, and 29 control subjects. We measured helium‐3 diffusion values at diffusion times from 0.23 to 1.97 s.

Results

One‐way analysis of variance revealed that the mean area under the helium‐3 diffusion curves (ADC AUC) of the smokers was significantly elevated compared with the controls and to the exposure‐to‐secondhand‐smoke subjects (P < 0.001 both). No difference between the mean ADC AUC of the exposure‐to‐secondhand‐smoke subjects and that of the controls was found (P = 0.115). However, application of a receiver operator characteristic‐derived rule to classify subjects as either a “control” or a “smoker,” based on ADC AUC, revealed that 30% (11/37) of the exposure‐to‐secondhand subjects were classified as “smokers” indicating an elevation of the ADC AUC.

Conclusion

Using helium‐3 diffusion MR, elevated ADC values were detected in 30% of nonsmoking healthy subjects who had been regularly exposed to secondhand smoke, supporting the concept that, in susceptible individuals, secondhand smoke causes mild lung damage. J. Magn. Reson. Imaging 2014;39:77–84. © 2013 Wiley Periodicals, Inc.
Breast MRI at 7 Tesla with a bilateral coil and robust fat suppression
Authors: Brown Ryan , Storey Pippa , Geppert Christian , McGorty KellyAnne , Klautau Leite Ana Paula , Babb James , Sodickson Daniel K. , Wiggins Graham C. , Moy Linda
Published: October 2013

Purpose

To develop a bilateral coil and fat suppressed T1‐weighted sequence for 7 Tesla (T) breast MRI.

Materials and Methods

A dual‐solenoid coil and three‐dimensional (3D) T1w gradient echo sequence with B1+ insensitive fat suppression (FS) were developed. T1w FS image quality was characterized through image uniformity and fat–water contrast measurements in 11 subjects. Signal‐to‐noise ratio (SNR) and flip angle maps were acquired to assess the coil performance. Bilateral contrast‐enhanced and unilateral high resolution (0.6 mm isotropic, 6.5 min acquisition time) imaging highlighted the 7T SNR advantage.

Results

Reliable and effective FS and high image quality was observed in all subjects at 7T, indicating that the custom coil and pulse sequence were insensitive to high‐field obstacles such as variable tissue loading. 7T and 3T image uniformity was similar (P = 0.24), indicating adequate 7T B1+ uniformity. High 7T SNR and fat–water contrast enabled 0.6 mm isotropic imaging and visualization of a high level of fibroglandular tissue detail.

Conclusion

7T T1w FS bilateral breast imaging is feasible with a custom radiofrequency (RF) coil and pulse sequence. Similar image uniformity was achieved at 7T and 3T, despite different RF field behavior and variable coil–tissue interaction due to anatomic differences that might be expected to alter magnetic field patterns. J. Magn. Reson. Imaging 2014;39:540–549. © 2013 Wiley Periodicals, Inc.
Impact of repetitive exposure to strong static magnetic fields on pregnancy and embryonic development of mice
Authors: Zahedi Yasmin , Zaun Gregor , Maderwald Stefan , Orzada Stephan , Pütter Carolin , Scherag André , Winterhager Elke , Ladd Mark E. , Grümmer Ruth
Published: October 2013

Purpose

To evaluate possible risks of strong static magnetic fields for embryo implantation, gestation, organogenesis, and embryonic development.

Materials and Methods

Pregnant mice were exposed for 75 minutes daily during the entire course of pregnancy at the bore entrance, representing the position of medical staff, and at the isocenter, representing the position of patients, of a 1.5 T and a 7 T human MRI scanner.

Results

No effect of static magnetic field strength was observed with regard to pregnancy rate, duration of pregnancy, litter size, still births, malformations, sex distribution, or postpartum death of offspring. During the first 8 weeks postnatal, mice exposed in utero to a magnetic field strength of 1.5 T or stronger showed a slight delay in weight gain and in time to eye opening compared to controls.

Conclusion

Daily exposure to strong magnetic fields during pregnancy had no deleterious effect on offspring; however, a developmental retardation could be observed postnatally with regard to weight gain and eye opening. J. Magn. Reson. Imaging 2014;39:691–699. © 2013 Wiley Periodicals, Inc.
Correction of B0‐Distortions in Echo‐Planar‐Imaging–Based Perfusion‐Weighted MRI
Authors: Vardal Jonas , Salo Raimo A. , Larsson Christopher , Dale Anders M. , Holland Dominic , Groote Inge Rasmus , Bjørnerud Atle
Published: October 2013

Purpose

To evaluate and quantify a scheme for correcting susceptibility artifacts in spin‐echo echo‐planar‐imaging–based dynamic susceptibility contrast (DSC) perfusion MRI of high‐grade gliomas at 3 Tesla.

Materials and Methods

Sixteen patients with a total of 78 scans were studied. DSC‐MRI images were corrected using a displacement map generated from opposite phase‐encoding polarity images. Two methods were used for quantification in the correction: (i) linear regression of pixel‐by‐pixel comparisons, performed both globally and relative to the anterior and posterior commissure plane (AC‐PC plane), of T2‐weighted images with both corrected and uncorrected raw DSC images; and (ii) counting significant (>2.0) normalized cerebral blood volume (nCBV) pixels from perfusion maps in the tumor region of interest.

Results

Sixty‐four of 78 datasets showed significant differences in the coefficient of correlation (r2) values. The difference between corrected and uncorrected r2 values was positive in all but one patient. Correction of B0‐ distortion significantly improved r2 in slices around the AC‐PC plane. In 62% of the datasets, we observed an increased number of significant pixels in the corrected nCBV maps; 36% showed more significant pixels in uncorrected nCBV maps; 1% showed no difference.

Conclusion

Distortion correction of DSC‐MRI may provide improved accuracy compared with uncorrected data, especially for tumors located below the corpus callosum and near the frontal sinuses. J. Magn. Reson. Imaging 2014;39:722–728. © 2013 Wiley Periodicals, Inc.
Sclerotic lesions of the spine: MRI assessment
Authors: Mugera Charles , Suh Kyung J. , Huisman Thierry A.G.M. , Weber Kristi , Belzberg Allan J. , Carrino John A. , Chhabra Avneesh
Published: October 2013

Sclerotic (T2 dark) lesions of the spine are infrequent and, as a result, these are often missed or misdiagnosed. Plain films may not be always available during magnetic resonance imaging (MRI) readout. Knowledge of such lesions and their imaging appearances on MRI evaluation is essential for a reader. Additionally, a systematic approach is important to accurately diagnose these lesions. In this article we discuss the various causes of spinal sclerotic lesions, describe their MRI characteristics with relevant case examples, and outline a systematic approach to their evaluation. J. Magn. Reson. Imaging 2013;38:1310–1324. © 2013 Wiley Periodicals, Inc.
Dynamic gadoxetate‐enhanced MRI for the assessment of total and segmental liver function and volume in primary sclerosing cholangitis
Authors: Nilsson Henrik , Blomqvist Lennart , Douglas Lena , Nordell Anders , Jacobsson Hans , Hagen Karin , Bergquist Annika , Jonas Eduard
Published: October 2013

Purpose

To evaluate dynamic hepatocyte‐specific contrast‐enhanced MRI (DHCE‐MRI) for the assessment of global and segmental liver volume and function in patients with primary sclerosing cholangitis (PSC), and to explore the heterogeneous distribution of liver function in this patient group.

Materials and Methods

Twelve patients with primary sclerosing cholangitis (PSC) and 20 healthy volunteers were examined using DHCE‐MRI with Gd‐EOB‐DTPA. Segmental and total liver volume were calculated, and functional parameters (hepatic extraction fraction [HEF], input relative blood‐flow [irBF], and mean transit time [MTT]) were calculated in each liver voxel using deconvolutional analysis. In each study subject, and incongruence score (IS) was constructed to describe the mismatch between segmental function and volume. Among patients, the liver function parameters were correlated to bile duct obstruction and to established scoring models for liver disease.

Results

Liver function was significantly more heterogeneously distributed in the patient group (IS 1.0 versus 0.4). There were significant correlations between biliary obstruction and segmental functional parameters (HEF rho −0.24; irBF rho −0.45), and the Mayo risk score correlated significantly with the total liver extraction capacity of Gd‐EOB‐DTPA (rho −0.85).

Conclusion

The study demonstrates a new method to quantify total and segmental liver function using DHCE‐MRI in patients with PSC. J. Magn. Reson. Imaging 2014;39:879–886. © 2013 Wiley Periodicals, Inc.
Method to create regional mechanical dyssynchrony maps from short‐axis cine steady‐state free‐precession images
Authors: Suever Jonathan D. , Fornwalt Brandon K. , Neuman Lee R. , Delfino Jana G. , Lloyd Michael S. , Oshinski John N.
Published: October 2013

Purpose

To develop a robust method to assess regional mechanical dyssynchrony from cine short‐axis MR images. Cardiac resynchronization therapy (CRT) is an effective treatment for patients with heart failure and evidence of left‐ventricular (LV) dyssynchrony. Patient response to CRT is greatest when the LV pacing lead is placed in the most dyssynchronous segment. Existing techniques for assessing regional dyssynchrony require difficult acquisition and/or postprocessing. Our goal was to develop a widely applicable and robust method to assess regional mechanical dyssynchrony.

Materials and Methods

Using the endocardial boundary, radial displacement curves (RDCs) were generated throughout the LV. Cross‐correlation was used to determine the delay time between each RDC and a patient‐specific reference. Delay times were projected onto the American Heart Association 17‐segment model creating a regional dyssynchrony map. Our method was tested in 10 normal individuals and 10 patients enrolled for CRT (QRS > 120 ms, NYHA III‐IV, EF < 35%).

Results

Delay times over the LV were 23.9 ± 33.8 ms and 93.1 ± 99.9 ms (P < 0.001) in normal subjects and patients, respectively. Interobserver reproducibility for segment averages was 6.8 ± 39.3 ms and there was 70% agreement in identifying the latest contracting segment.

Conclusion

We have developed a method that can reliably calculate regional delay times from cine steady‐state free‐precession (SSFP) images. Maps of regional dyssynchrony could be used to identify the latest‐contracting segment to assist in CRT lead implantation. J. Magn. Reson. Imaging 2014;39:958–965. © 2013 Wiley Periodicals, Inc.
Quantitative MRI of articular cartilage and its clinical applications
Authors: Li Xiaojuan , Majumdar Sharmila
Published: October 2013

Cartilage is one of the most essential tissues for healthy joint function and is compromised in degenerative and traumatic joint diseases. There have been tremendous advances during the past decade using quantitative MRI techniques as a noninvasive tool for evaluating cartilage, with a focus on assessing cartilage degeneration during osteoarthritis (OA). In this review, after a brief overview of cartilage composition and degeneration, we discuss techniques that grade and quantify morphologic changes as well as the techniques that quantify changes in the extracellular matrix. The basic principles, in vivo applications, advantages, and challenges for each technique are discussed. Recent studies using the OA Initiative (OAI) data are also summarized. Quantitative MRI provides noninvasive measures of cartilage degeneration at the earliest stages of joint degeneration, which is essential for efforts toward prevention and early intervention in OA. J. Magn. Reson. Imaging 2013;38:991–1008. © 2013 Wiley Periodicals, Inc.
Fully automated tool to identify the aorta and compute flow using phase‐contrast MRI: Validation and application in a large population based study
Authors: Goel Akshay , McColl Roderick , King Kevin S. , Whittemore Anthony , Peshock Ronald M.
Published: October 2013

Purpose

To assess if fully automated localization of the aorta can be achieved using phase contrast (PC) MR images.

Materials and Methods

PC cardiac‐gated MR images were obtained as part of a large population‐based study. A fully automated process using the Hough transform was developed to localize the ascending aorta (AAo) and descending aorta (DAo). The study was designed to validate this technique by determining: (i) its performance in localizing the AAo and DAo; (ii) its accuracy in generating AAo flow volume and DAo flow volume; and (iii) its robustness on studies with pathological abnormalities or imaging artifacts.

Results

The algorithm was applied successfully on 1884 participants. In the randomly selected 50‐study validation set, linear regression shows an excellent correlation between the automated (A) and manual (M) methods for AAo flow (r = 0.99) and DAo flow (r = 0.99). Bland‐Altman difference analysis demonstrates strong agreement with minimal bias for: AAo flow (mean difference [A‐M] = 0.47 ± 2.53 mL), and DAo flow (mean difference [A‐M] = 1.74 ± 2.47 mL).

Conclusion

A robust fully automated tool to localize the aorta and provide flow volume measurements on phase contrast MRI was validated on a large population‐based study. J. Magn. Reson. Imaging 2014;40:221–228. © 2013 Wiley Periodicals, Inc.
Three‐dimensional assessment of lung tissue density using a clinical ultrashort echo time at 3 tesla: A feasibility study in healthy subjects
Authors: Lederlin Mathieu , Crémillieux Yannick
Published: October 2013

Purpose

To implement and assess the performance of three‐dimensional (3D) ultra‐short echo (UTE) time for evaluating lung tissue density changes induced by gravity dependence and lung inflation.

Materials and Methods

Twelve healthy volunteers were imaged by 3D UTE at 3 Tesla, during free‐breathing and breathholding of the subjects. MR signal intensities were measured in lung tissue and muscle regions. The variations of MR lung signal intensity and lung water content were evaluated as a function of lung inflation and anterior/posterior position.

Results

SNR in lung tissue ranged between 35 for free‐breathing acquisitions and 7 for breathhold acquisitions at functional residual capacity. Lung‐to‐muscle signal ratios decreased from 0.58 in posterior areas to 0.34 in anterior areas. The average water content measured in lungs was equal to 34% and 58% in gravitationally nondependent and dependent regions of interest.

Conclusion

The 3D UTE lung MRI provides signal within lung parenchyma and can be used to assess lung tissue density. J. Magn. Reson. Imaging 2014;40:839–847. © 2013 Wiley Periodicals, Inc.
CD81 sequence and susceptibility to hepatitis C infection
Authors: Houldsworth Annwyne , Metzner Magdalena M. , Demaine Andrew , Hodgkinson Andrea , Kaminski Edward , Cramp Matthew
Published: October 2013

Several cell surface molecules have hepatitis C virus (HCV) binding properties and may serve as receptors facilitating viral entry into cells. The large extracellular loop (LEL) of CD81 has been shown to bind the HCV envelope protein E2 with several critical residues for the CD81‐HCV‐E2 interaction. It was hypothesised that variation in the CD81 LEL sequence may modify susceptibility to HCV infection. HCV RNA negative patients with spontaneous viral clearance (RNA −ve); HCV RNA positive cases, who are affected chronically (RNA +ve); and patients at high risk of HCV infection, exposed but uninfected patients (EU) were studied. Genomic DNA was extracted from whole blood samples and four exons of the CD81 LEL gene were amplified by PCR and sequenced. The cDNA derived from CD81 (≈700 bp) was sequenced following RNA extraction from peripheral blood mononuclear cells. Patients, who are RNA positive, RNA negative, and exposed uninfected were sequenced for four DNA sections (A, B, C, and D). Sixty‐two (43M:19F) patients, from all the patient cohorts, were sequenced and compared for the C section alone (which encompasses the important binding region of the molecule for envelope protein) including 21 (14M:7F) HCV RNA negative, 15 (10M:5F) HCV RNA positive and 26 (20M:6F) exposed uninfected and no sequence differences were observed. The entire CD81 sequence from cDNA was obtained in 23 cases—11 RNA −ve, 5 RNA +ve and 7 EU. In 7 of the 23 cases, the nucleotides were confirmed with the genomic sequence (4 RNA −ve and 3 EU cases). No sequence variation was found in any of the patients studied by either method, including gene sections encoding the residues most important for CD81‐HCV E2 binding. The LEL of CD81 is a molecule that is highly conserved. No differences in nucleotide sequence influencing susceptibility to, or outcome of HCV infection or evidence of methylation of the gene were found. J. Med. Virol. 86:162–168, 2014. © 2013 Wiley Periodicals, Inc.
Residual viremia in patients on antiretroviral therapy incorporating nevirapine is not associated with the gag‐specific cellular immune response
Authors: McIlroy Dorian , Allavena Clotilde , Rodallec Audrey , Billaud Eric , Ferré Virginie , Raffi François
Published: October 2013

To determine whether residual plasma viremia in HIV+ patients on nevirapine‐including antiretroviral therapy (ART) is related to anti‐HIV cellular immune responses, a case–control study was conducted comparing residual viremia in patients with detectable and undetectable Gag‐specific T‐cell responses. Gag‐specific responses were measured by IFN‐γ ELISpot. Residual viremia was determined at two consecutive hospital visits by an ultra‐sensitive technique with a detection limit of 2 copies/ml. Median residual viremia was not different in patients with a positive Gag‐specific ELISpot (n = 25) compared to those with a negative Gag‐specific ELISpot (n = 30, P = 0.91). Ten of 25 (40%) patients with consistent detectable residual viremia and 4 of 12 (33%) patients with consistently undetectable residual viremia had a positive Gag‐specific ELISpot. Undetectable residual viremia was associated with the duration of ART including nevirapine (P < 0.05), but not with the Gag‐specific ELISpot response. Gag‐specific CTL in patients on ART therefore appear to have no impact on the virus‐producing cells that are responsible for residual viremia during ART. J. Med. Virol. 86:1087–1092, 2014. © 2013 Wiley Periodicals, Inc.
Local and global spatio‐temporal dynamics of HIV‐1 subtype F1
Authors: Lai Alessia , Ciccozzi Massimo , Franzetti Marco , Simonetti Francesco R. , Bozzi Giorgio , Binda Francesca , Rosi Andrea , Bonora Stefano , De Luca Andrea , Balotta Claudia , Zehender Gianguglielmo
Published: October 2013

Previous studies have attempted to explore the origin of the F1 subtype, but the precise origin of the Romanian and South American F1 variants remains controversial. As the F1 subtype is the most frequent non‐B variant among Europeans residing in Italy, the aim of this study was to estimate its phylogeography in order to reconstruct its origin and route of dispersion. The phylogeographical analyses, which were made using the Bayesian Markov Chain Monte Carlo approach and BEAST software, revealed two significant clades: the first included all of the Romanian strains together with a few Italian and four African isolates; the second encompassed all of the South American sequences and the large majority of Italian variants. By putting the African reference sequences into two discrete groups based on specific countries, phylogeographic analysis indicated that the F1 epidemic originated in Cameroon/Democratic Republic of Congo in the early 1940s, and was exported to South America 10 years later. Subsequently, the F1 virus spread to Angola and, from there, was exported to Romania in the early 1960s. It reached Italy in the 1970s from South America and Romania. The South American and Romanian variants of F1 have different African countries of origin and different temporal spreads. The South American variant seems to be characterized by multiple introduction events, whereas the Romanian strain probably spread as a result of a single entry. Two different pathways from South America and Romania led the F1 variant to Italy in the 1970s. J. Med. Virol. 86:186–192, 2014. © 2013 Wiley Periodicals, Inc.
Human caliciviruses detected in HIV‐seropositive children in Kenya
Authors: Mans Janet , Murray Tanya Y. , Kiulia Nicholas M. , Mwenda Jason M. , Musoke Rachel N. , Taylor Maureen B.
Published: October 2013

The human caliciviruses (HuCVs) are important causes of gastroenteritis worldwide. Norovirus (NoV) and sapovirus (SaV) have been detected in HIV‐seropositive children but the genetic diversity of HuCVs circulating in these individuals is largely unknown. In this study the prevalence and genotype diversity of HuCVs circulating in Kenyan HIV‐positive children, with or without diarrhea, from the year 1999 to 2000 was investigated. The overall prevalence of HuCVs was 19% with NoV predominating at 17% (18/105) and SaV present in 5.7% (6/105) of specimens. Human CVs were detected in both symptomatic (24%) and asymptomatic (16%) children. Co‐infections with other enteric viruses were detected in 21.6% of children with diarrhea but only in 4.4% of children without diarrhea. Remarkable genetic diversity was observed with 12 genotypes (7 NoV, 5 SaV) being identified in 20 HuCV‐infected children. NoV genogroup II (GII) strains predominated with GII.2 and GII.4 each representing 27% of the NoV‐positive strains. The GII.4 strain was most closely related to the nonepidemic GII.4 Kaiso 2003 variant. Other NoV genotypes detected were GI.3, GII.6, GII.12, GII.14, and GII.17. Five different SaV genotypes (GI.2, GI.6, GII.1, GII.2, and GII.4) were characterized from six specimens. Diarrheal symptoms were not associated with any specific HuCV genotype. Overall the HuCV genotype distribution detected in this study reflects those in other studies worldwide. The strains detected are closely related to genotypes that have circulated on several continents since the year 2000. J. Med. Virol. 86:75–81, 2014. © 2013 Wiley Periodicals, Inc.