bluuebunny/crossref_metadata_2025 huggingface dataset:
Low loss and frequency (1 kHz–1 MHz) independent dielectric characteristics of 3BaO–3TiO2–B2O3 glasses
Authors: Vaish Rahul , Varma K. B. R.
Published: December 2009

X-ray powder diffraction along with differential thermal analysis carried out on the as-quenched samples in the 3BaO–3TiO2–B2O3 system confirmed their amorphous and glassy nature, respectively. The dielectric constants in the 1 kHz–1 MHz frequency range were measured as a function of temperature (323–748 K). The dielectric constant and loss were found to be frequency independent in the 323–473 K temperature range. The temperature coefficient of dielectric constant was estimated using Havinga’s formula and found to be 16 ppm K−1. The electrical relaxation was rationalized using the electric modulus formalism. The dielectric constant and loss were 17±0.5 and 0.005±0.001, respectively at 323 K in the 1 kHz–1 MHz frequency range which may be of considerable interest to capacitor industry.
Cavity dumping of an injection-locked free-electron laser
Authors: Takahashi Susumu , Ramian Gerald , Sherwin Mark S.
Published: December 2009

This letter reports cavity dumping of an electrostatic-accelerator-driven free-electron laser (FEL), while it is injection-locked to a frequency-stabilized 240 GHz solid-state source. Cavity dumping enhances the FEL output power by a factor of ∼8, and abruptly cuts off the end of the FEL pulse. The cavity-dumped, injection-locked FEL output is used in a 240 GHz pulsed electron spin resonance experiment.
High remnant polarization in (Sr0.7Bi0.2)TiO3–(Na0.5Bi0.5)TiO3 solid solutions
Authors: Ang Chen , Yu Zhi
Published: December 2009

The dielectric and ferroelectric properties of (1-z) (Sr0.7Bi0.2)TiO3–z(Na0.5Bi0.5)TiO3 solid solutions with z=0.65–1 are studied. High remnant polarization of ∼51 μC/cm2 with a coercive field of 50 kV/cm, and a dielectric constant of ∼1000 have been obtained at room temperature in the sample with z=0.9, indicating an application potential as a lead-free ferroelectric material. There are two dielectric anomalies in the temperature range of 150–670 K for all samples; one is the dielectric peak without significant frequency dispersion, and the other is significantly frequency dependent. The result of this work shows that the formula scheme “a ferroelectric relaxor+a ferroelectric” for solid solutions is a promising approach in the search for high performance lead-free ferroelectric materials.
Gaussian approximation for the structure function in semiclassical forward-backward initial value representations of time correlation functions
Authors: Tao Guohua , Miller William H.
Published: December 2009

Initial value representations (IVRs) of semiclassical (SC) theory provide a general approach for adding quantum mechanical effects to classical molecular dynamics simulations of large molecular systems. Of the various versions of SC-IVR methodology for evaluating time correlation functions, the Fourier transform forward-backward (FB) approach is the simplest one that is able to describe true quantum coherence effects, so it is of considerable importance to find efficient and systematic ways for implementing it. It is shown in this paper that a Gaussian approximation for the “structure function”—the dependence of the correlation function on the (typically) momentum jump parameter—provides an efficient and accurate way for doing so. The approach is illustrated by an application to the time-dependent radial distribution function of I2 (after photoexcitation) in a cluster of (up to 16) argon atoms.
Light harvesting complex II B850 excitation dynamics
Authors: Strümpfer Johan , Schulten Klaus
Published: December 2009

The dynamics of excitation energy transfer within the B850 ring of light harvesting complex 2 from Rhodobacter sphaeroides and between neighboring B850 rings is investigated by means of dissipative quantum mechanics. The assumption of Boltzmann populated donor states for the calculation of intercomplex excitation transfer rates by generalized Förster theory is shown to give accurate results since intracomplex exciton relaxation to near-Boltzmann population exciton states occurs within a few picoseconds. The primary channels of exciton transfer between B850 rings are found to be the five lowest-lying exciton states, with non-850 nm exciton states making significant contributions to the total transfer rate.
Size-effects on the optical properties of zirconium oxide thin films
Authors: Ramana C. V. , Vemuri R. S. , Fernandez I. , Campbell A. L.
Published: December 2009

Zirconium oxide (ZrO2) thin films with an average crystallite-size (L) ranging from 5 to 25 nm were grown by sputter deposition onto optical grade quartz substrates. The optical properties of grown ZrO2 films were evaluated using optical transmission and reflectance spectroscopic measurements. The size-effects were significant on the optical characteristics of ZrO2 films. The bandgap energy (Eg) was found to increase from 5.78 to 6.07 eV with decreasing L values from 20 to 7 nm. A direct, linear inverse L-Eg relationship found for ZrO2 films suggest that tuning optical properties for desired applications can be achieved by controlling the size.
Large magnetoresistance of thick polymer devices having La0.67Sr0.33MnO3 electrodes
Authors: Ozbay A. , Nowak E. R. , Yu Z. G. , Chu W. , Shi Yijian , Krishnamurthy S. , Tang Z. , Newman N.
Published: December 2009

We report magnetoresistance (MR) measurements for structures with micrometer-thick regioregular, polythiophene (rr-P3HT) polymer layers between two ferromagnetic contacts. Hole spin transport through the polymer layer leads to a relative MR value in 300 mT fields of 0.3% at 300 K and increasing to 18% at 25 K. The inferred intrinsic spin lifetime and diffusion length are about 7 ms and 0.4 μm, respectively. The spin transport coherence length is enhanced by the electric field, leading to an enhancement in MR with increasing applied voltage.
Gas adsorption on graphene doped with B, N, Al, and S: A theoretical study
Authors: Dai Jiayu , Yuan Jianmin , Giannozzi Paolo
Published: December 2009

The adsorption of several common gas molecules over boron-, nitrogen-, aluminum-, and sulfur-doped graphene was theoretically studied using density-functional theory. B- and N-doped graphene retain a planar form, while Al and S atoms protrude out of the graphene layer. We find that only NO and NO2 bind to B-doped graphene, while only NO2 binds to S-doped graphene. Al-doped graphene is much more reactive and binds many more gases, including O2. We suggest that B- and S-doped graphene could be a good sensor for polluting gases such as NO and NO2.
A robust approach to calculate entropy change based on density functional theory in the energy representation
Authors: Yokogawa Daisuke , Ikegami Takahisa
Published: December 2009

We have developed a new approach to accurately calculate entropy change based on density functional theory in the energy representation. The entropy change was evaluated using the derived equation and energy distributions computed using molecular simulation and reweighting techniques. This approach was applied to a harmonic oscillator, an alanine dipeptide, and a small protein. We found that the results were accurate compared to conventional approaches, such as the quasiharmonic approximation.
Epitaxial fabrication and memory effect of ferroelectric LiNbO3 film/AlGaN/GaN heterostructure
Authors: Hao Lanzhong , Zhu Jun , Luo Wenbo , Zeng Huizhong , Li Yanrong , Huang Wen , Liao Xiuwei , Zhang Ying
Published: December 2009

A metal-ferroelectric-semiconductor structure was fabricated epitaxially by depositing a LiNbO3 film on the surface of the AlGaN/GaN template with two dimensional electron gas (2DEG). The capacitance-voltage characteristics were studied. Counterclockwise memory windows could be observed clearly. The size of the window first increased with increasing forward bias (Vmax) and reached a maximum of 2.5 V when Vmax=6 V. This was attributed to the switchable ferroelectric polarization modulating on 2DEG. When Vmax exceeded 6 V, the window decreased due to electron injection. These results indicated that ferroelectric films combined with AlGaN/GaN would hold promise for next-generation memory devices.
Frontside illuminated TiO2 nanotube dye-sensitized solar cells using multifunctional microchannel array electrodes
Authors: Liu Yong , Wang Hai , Li Ming , Hong Ruijiang , Ye Qihong , Zheng Jiemin , Shen Hui
Published: December 2009

Here we report a frontside illuminated TiO2 nanotube based dye-sensitized solar cell (DSSC). The photoanode with inclined microchannels (IMCs) formed by laser drilling acted as a multifunctional role for enhancing the cell’s efficiency; light trapping, pathway for transporting electrolyte, and extra surface area for dye loading. The amount of N719 dye absorbed on IMCs photoanode was measured to be 3.83×10−7 mol/cm2, which was almost 1.82 times as high as that of the flat photoanode. The frontside illuminated DSSC showed an energy conversion efficiency of 4.1% under AM1.5 condition, which was much higher compared to that (3.1%) of the backside illuminated DSSC.
Magnetothermal cooling with a phase separated manganite
Authors: Rebello A. , Mahendiran R.
Published: December 2009

We show that temperature of a current (I=20 mA) carrying manganite (Nd0.5Ca0.5Mn0.93Ni0.07O3) in presence of a magnetic field (H) decreases abruptly as much as ΔT=45 K (7 K) accompanied by a steplike decrease in magnetoresistance at a critical value of H when the base temperature is 40 K (100 K). The magnitude of ΔT and the position of magnetoresistance step decrease toward lower H with decreasing amplitude of the current. We discuss possible origins of the current and magnetic-field driven temperature change which may find applications in magnetothermal refrigeration besides magnetocaloric effect.
Corrugated-sidewall interband cascade lasers with single-mode midwave-infrared emission at room temperature
Authors: Kim C. S. , Kim M. , Bewley W. W. , Lindle J. R. , Canedy C. L. , Abell J. , Vurgaftman I. , Meyer J. R.
Published: December 2009

We report interband cascade lasers operating in a single spectral mode (λ≈3.6 μm) at −5–30 °C. A corrugated pattern etched into both sidewalls of the 6- and 9-μm-wide ridges serves to suppress higher-order lateral modes by increasing their loss, and also provides a fourth-order distributed-feedback grating for longitudinal mode selection. Despite the grating’s weak coupling strength, the 9 μm ridge produced up to 12 mW per facet of single-mode cw output power at 25 °C, with a side-mode suppression ratio of >30 dB.
Synthesis of CuInS2 Microspheres using In2S3 Microspheres as Templates
Authors: Ge Ming , Guo Changsheng , Liu Lu , Zhang Baoquan , Zhou Zhen
Published: December 2009

CuInS2 microspheres have been prepared via a solvothermal route employing synthetic In2S3 microspheres as templates. X-ray diffraction analysis reveals that CuInS2 crystals assembled from In2S3 microsphere building blocks are tetragonal phase. Field emission scanning electron microscopy and transmission electron microscopy images show that the prepared CuInS2 microspheres are constructed by nanosheets. The evolution of crystal structure could be attributed to Cu+ ions inserted into the In2S3 microsphere templates, such that some In3+ ions were replaced and tetragonal CuInS2 crystals were formed during the solvothermal process.
A 'Butterfly'-shaped Water Tetramer in a Cu4 Complex Supported by a Hydrazone Ligand: Synthesis, Crystal Structure, Magnetic Properties, and Quantum Chemical Study
Authors: Banerjee Sambuddha , Sen Soma , Chakraborty Joy , Butcher Ray J. , García Carlos J. Gómez , Puchta Ralph , Mitra Samiran
Published: December 2009

A potentially tetradentate NOOO donor hydrazone ligand, LH2 (condensation product of benzhydrazide with O-vanillin) generates a tetranuclear CuII complex [Cu4(L)4]·4H2O (1), whose void spaces are occupied by water tetramers presenting a ‘butterfly’ conformation with the highest dihedral angle reported to date, as revealed by its X-ray crystal structure. 1 has also been characterized using various spectroscopic techniques, including IR, UV-vis, and elemental analysis. Variable temperature magnetic susceptibility measurements reveal the presence of moderate antiferromagnetic intra-tetramer coupling between the four CuII centres connected through simple oxo groups of the hydrazone ligand with two different coupling constants (J1
= –61.7(3) cm–1 and J2
= –92(1) cm–1) corresponding to the two different CuII tetramers identified in the X-ray structure. We also report a quantum chemical study (MP2(full)/6–311+G(3df,2p)//B3LYP/6–311+G(3df,2p)) to calculate the stability of the water tetramers.
Spatial and temporal extremes of wildfire sizes in Portugal (1984–2004)
Authors: de Zea Bermudez P. , Mendes J. , Pereira J. M. C. , Turkman K. F. , Vasconcelos M. J. P.
Published: December 2009

Spatial and temporal patterns of large fire (>100 ha) incidence in Portugal over the period 1984–2004 were modeled using extreme value statistics, namely the Peaks Over Threshold approach, which uses the Generalized Pareto Distribution (GPD) as a model. The original dataset includes all fires larger than 5 ha (30 616 fires) that were observed in Portugal during the study period, mapped from Landsat satellite imagery. The country was divided into eight regions, considered internally homogeneous from the perspective of their fire regimes and respective environmental correlates. The temporal analysis showed that there does not appear to be any trend in the incidence of very large fires, but revealed a cyclical behavior in the values of the GPD shape parameter, with a period in the range of 3 to 5 years. Spatial analysis highlighted strong regional differences in the incidence of large fires, and allowed the calculation of return levels for a range of fire sizes. This analysis was affected by the presence of a few outlying observations, which may correspond to clusters of contiguous fire scars, resulting in artificially large burned areas. We discuss some of the implications of our findings in terms of consequences for fire management aimed at preventing the occurrence of extremely large fires, and present ideas for extending the present study.
Road network density correlated with increased lightning fire incidence in the Canadian western boreal forest
Authors: Arienti M. Cecilia , Cumming Steven G. , Krawchuk Meg A. , Boutin Stan
Published: December 2009

This paper quantifies the influence of anthropogenic linear disturbances on fire ignition frequency in the boreal forests of western Canada. Specifically, we tested if linear features increase the frequency of lightning fires, and whether this relationship is affected by spatial resolution. We considered fires that ignited between 1995 and 2002 within a ~67 000 km2 region of boreal mixed-wood forest in north-eastern Alberta where linear features are highly abundant and spatially heterogeneous. We constructed Poisson, Negative Binomial and Zero-Inflated Poisson models at two spatial resolutions (~10 000 and ~2400 ha), including covariates for linear feature densities, forest composition, weather–lightning indices and geography. We found a positive association between lightning fire frequency and road density; this association was consistent at both spatial resolutions. We suggest this occurs owing to increased availability of flammable fine fuels near roads. The effect was attributable neither to increased detectability of fires proximal to roads by human observers, nor to increased lightning strikes due to metallic infrastructure alongside roads or the topographic characteristics of road location. Our results suggest that, in the face of projected road developments in the region, the potential exists for important changes to the regional fire regime. Further research should elucidate the precise mechanisms in order to develop methods for mitigation.
Critical live fuel moisture in chaparral ecosystems: a threshold for fire activity and its relationship to antecedent precipitation
Authors: Dennison Philip E. , Moritz Max A.
Published: December 2009

Large wildfires in southern California typically occur during periods of reduced live fuel moisture (LFM) and high winds. Previous work has found evidence that a LFM threshold may determine when large fires can occur. Using a LFM time series and a fire history for Los Angeles County, California, we found strong evidence for a LFM threshold near 79%. Monthly and 3-month total precipitation data were used to show that the timing of this threshold during the fire season is strongly correlated with antecedent rainfall. Spring precipitation, particularly in the month of March, was found to be the primary driver of the timing of LFM decline, although regression tree analysis revealed that high winter precipitation may delay the timing of the threshold in some years. This work further establishes relationships between precipitation and fire potential that may prove important for anticipating shifts in fire regimes under climate-change scenarios.
Characterization of wildfire regimes in Canadian boreal terrestrial ecosystems
Authors: Jiang Yueyang , Zhuang Qianlai , Flannigan Mike D. , Little John M.
Published: December 2009

Wildfire is a major disturbance in boreal terrestrial ecosystems. Characterizing fire regimes and projecting fire recurrence intervals for different biomes are important in managing those ecosystems and quantifying carbon dynamics of those ecosystems. This study used Canadian wildfire datasets, 1980–1999, to characterize relationships between number of fires and burned area for 13 ecozones and to calculate wildfire recurrence intervals in each ecozone. For the study period, wildfires were found to follow power–law relationships between frequency densities (number of fires normalized to unit bins) and burned areas in all ecozones. Power–law frequency–area relationships also held for both anthropogenic fires and natural fires in the 1980s and 1990s. For each Canadian ecozone using the parameters of the power–law frequency–area distributions, fire recurrence intervals were then calculated for wildfires equal to or larger than a given size of burned area. Fire recurrence intervals ranged from 1 to 32 years for burned areas >2 km2, and from 1 to 100 years for burned areas >10 km2 in every 10 000-km2 spatial area for each ecozone. The information obtained through characterizing the wildfires and the fire recurrence intervals calculated in this study will provide guidance to wildfire risk managers throughout Canada. The findings of this study will also be a benefit to future efforts in quantifying carbon dynamics in Canadian boreal terrestrial ecosystems.
The Great American Biotic Interchange in birds
Authors: Weir Jason T. , Bermingham Eldredge , Schluter Dolph
Published: December 2009

The sudden exchange of mammals over the land bridge between the previously isolated continents of North and South America is among the most celebrated events in the faunal history of the New World. This exchange resulted in the rapid merging of continental mammalian faunas that had evolved in almost complete isolation from each other for tens of millions of years. Yet, the wider importance of land bridge-mediated interchange to faunal mixing in other groups is poorly known because of the incompleteness of the fossil record. In particular, the ability of birds to fly may have rendered a land bridge unnecessary for faunal merging. Using molecular dating of the unique bird faunas of the two continents, we show that rates of interchange increased dramatically after land bridge completion in tropical forest-specializing groups, which rarely colonize oceanic islands and have poor dispersal abilities across water barriers, but not in groups comprised of habitat generalists. These results support the role of the land bridge in the merging of the tropical forest faunas of North and South America. In contrast to mammals, the direction of traffic across the land bridge in birds was primarily south to north. The event transformed the tropical avifauna of the New World.
Ejaculate components delay reproductive senescence while elevating female reproductive rate in an insect
Authors: Reinhardt Klaus , Naylor Richard A. , Siva-Jothy Michael T.
Published: December 2009

Increased female reproductive rates usually result in accelerated senescence. This correlation provides a link between the evolutionary conflict of the sexes and aging when ejaculate components elevate female reproductive rates at the cost of future reproduction. It is not clear whether this female cost is manifest as shorter lifespan or an earlier onset or a steeper rate of reproductive senescence. It also is unclear whether beneficial ejaculates release females from reproductive trade-offs and, if so, which senescence parameters are affected. We examined these issues in the bedbug,
Cimex lectularius
, a long-lived insect that shows reduced female lifespan as well as female reproductive senescence at the male-determined mating frequency. We demonstrate experimentally that, independently of the mating frequency, females receiving more ejaculate show increased reproductive rates and enter reproductive senescence later than females receiving less ejaculate. The rate of reproductive senescence did not differ between treatments, and reproductive rates did not predict mortality. The ejaculate effects were consistent in inter- and intra-population crosses, suggesting they have not evolved recently and are not caused by inbreeding. Our results suggest that ejaculate components compensate for the costs of elevated female reproductive rates in bedbugs by delaying the onset of reproductive senescence. Ejaculate components that are beneficial to polyandrous females could have arisen because male traits that protect the ejaculate have positive pleiotropic effects and/or because female counteradaptations to antagonistic male traits exceed the neutralization of those traits. That males influence female reproductive senescence has important consequences for trade-offs between reproduction and longevity and for studies of somatic senescence.
Alternative splicing and gene duplication differentially shaped the regulation of isochorismate synthase in
Populus
and
Arabidopsis
Authors: Yuan Yinan , Chung Jeng-Der , Fu Xueyan , Johnson Virgil E. , Ranjan Priya , Booth Sarah L. , Harding Scott A. , Tsai Chung-Jui
Published: December 2009

Isochorismate synthase (ICS) converts chorismate to isochorismate for the biosynthesis of phylloquinone, an essential cofactor for photosynthetic electron transport. ICS is also required for salicylic acid (SA) synthesis during
Arabidopsis
defense. In several other species, including
Populus
, SA is derived primarily from the phenylpropanoid pathway. We therefore sought to investigate
ICS
regulation in
Populus
to learn the extent of ICS involvement in SA synthesis and defense.
Arabidopsis
harbors duplicated
AtICS
genes that differ in their exon-intron structure, basal expression, and stress inducibility. In contrast, we found a single
ICS
gene in
Populus
and six other sequenced plant genomes, pointing to the
AtICS
duplication as a lineage-specific event. The
Populus ICS
encodes a functional plastidic enzyme, and was not responsive to stresses that stimulated phenylpropanoid accumulation.
Populus ICS
underwent extensive alternative splicing that was rare for the duplicated
AtICSs
. Sequencing of 184 RT-PCR
Populus
clones revealed 37 alternative splice variants, with normal transcripts representing ≈50% of the population. When expressed in
Arabidopsis
,
Populus ICS
again underwent alternative splicing, but did not produce normal transcripts to complement AtICS1 function. The splice-site sequences of
Populus ICS
are unusual, suggesting a causal link between junction sequence, alternative splicing, and ICS function. We propose that gene duplication and alternative splicing of
ICS
evolved independently in
Arabidopsis
and
Populus
in accordance with their distinct defense strategies.
AtICS1
represents a divergent isoform for inducible SA synthesis during defense.
Populus ICS
primarily functions in phylloquinone biosynthesis, a process that can be sustained at low
ICS
transcript levels.
Black soot and the survival of Tibetan glaciers
Authors: Xu Baiqing , Cao Junji , Hansen James , Yao Tandong , Joswia Daniel R. , Wang Ninglian , Wu Guangjian , Wang Mo , Zhao Huabiao , Yang Wei , Liu Xianqin , He Jianqiao
Published: December 2009

We find evidence that black soot aerosols deposited on Tibetan glaciers have been a significant contributing factor to observed rapid glacier retreat. Reduced black soot emissions, in addition to reduced greenhouse gases, may be required to avoid demise of Himalayan glaciers and retain the benefits of glaciers for seasonal fresh water supplies.
Biophysical model for gamma rhythms in the olfactory bulb via subthreshold oscillations
Authors: Brea Jorge N. , Kay Leslie M. , Kopell Nancy J.
Published: December 2009

Gamma oscillations in the olfactory bulb can be produced as an interaction of subthreshold oscillations (STOs) in the mitral cells (MCs) with inhibitory granule cells (GCs). The mechanism does not require that the GCs spike, and we work in a regime in which the MCs fire at rates lower than the fast gamma rhythm they create. The frequency of the network is that of the STOs, allowing the gamma to be modulated in amplitude with only small changes in frequency. Gamma oscillations could also be obtained with spiking GCs, but only for GCs firing close to population rate. Our mechanism differs from the more standard description of the gamma oscillation, in which the the decay time of the inhibitory cells is critical to the frequency of the network.
Vessel size estimation in peripheral artery interventions: are angiographic measurements reliable?
Authors: Stenström Hugo , Knutsson Anders , Smedby Örjan
Published: December 2009

Purpose: To describe and evaluate a new technique for angiographic measurement of arterial diameters and to make a comparison with other common techniques.

Material and Methods: The Angiometer has a radiopaque metal body with six cylindrical segments of varying diameter. Arterial diameter is estimated by visually relating the vessel to these segments. The measurements (method A) were compared: to measuring in relation to a ruler on the table‐top by means of compasses (B), to an automated measurement technique (quantitative angiography) utilizing calibration to a catheter of known diameter (C), and to a computer‐based distance measurement using the ruler on the table‐top as reference (D). Twenty‐five patients were studied. Each method was used twice by each of two independent observers. A phantom with four drilled holes, filled with contrast agent, was also studied.

Results: The coefficient of variation was highest for method C and lowest for method A. Correlations between readings were highest for method A and lowest for method C. Mean diameter values were highest for method A and lowest for methods B and D. In the phantom experiments, sizes were overestimated by between 5% and 9% with method A, and underestimated by between 4% and 27% with the other methods.

Conclusion: In terms of reproducibility and accuracy, the proposed method compares favorably with alternative methods.
Percutaneous vertebroplasty: indications, contraindications, technique, and complications
Authors: Guglielmi G. , Andreula C. , Muto M. , Gilula L. A.
Published: December 2009

Percutaneous vertebroplasty is emerging as one of the most promising new interventional procedures for relieving (or reducing) painful vertebra, with the injection of surgical polymethylmethacrylate or cement into vertebral bodies. This imaged‐guided technique, originally used to treat vertebral hemangioma, has recently been extended to the treatment of metastases, osteoporotic compression fractures, and vertebral myeloma. It is increasingly being accepted as a main treatment of choice in the management of resistant back pain due to vertebral compression fractures, especially in the elderly individual who is not a candidate for surgery. In this article, we review indications, contraindications, technique, and complications of percutaneous vertebroplasty.
Extrapedicular approach of percutaneous vertebroplasty in the treatment of upper and mid‐thoracic vertebral compression fracture
Authors: Han K.‐R. , Kim C. , Eun J.‐S. , Chung Y.‐S.
Published: December 2009

Purpose: To evaluate the clinical outcome of the extrapedicular approach of percutaneous vertebroplasty (PVP) for upper and mid‐thoracic vertebral compression fractures in patients.

Material and Methods: Extrapedicular vertebroplasty was performed in painful compression fractures at T4–T8 levels. The assessment criteria were changes over time in visual analog scale (VAS) and mobility score. We evaluated the volume of cement injected, the size of needle required, and complications.

Results: Procedures were performed in 27 patients with a total of 34 affected vertebral bodies. Early (within a week) and one year later, clinical follow‐ups showed that pain intensity had decreased by 50% one day after operation and later by 70–80%. Mobility scores of all patients were improved immediately after the procedure. Average volume of polymethylmethacrylate (PMMA) per vertebral body was 3.8±1.2 ml. Leakage of PMMA occurred in one vertebral level (intradiskal space), but did not cause clinical complications.

Conclusion: PVP of upper and mid‐thoracic spine with an extrapedicular approach is an efficient and safe procedure for treating painful thoracic vertebral compression fracture under a cautious patient selection and meticulous technical procedure.
Posterolateral complex knee injuries: magnetic resonance imaging with surgical correlation
Authors: Theodorou D. J. , Theodorou S. J. , Fithian D. C. , Paxton L. , Garelick D. H. , Resnick D.
Published: December 2009

Purpose: To describe the magnetic resonance imaging (MRI) findings of injuries of the posterolateral aspect of the knee and to evaluate the diagnostic capabilities of MRI in the assessment of these injuries.

Material and Methods: The MRI studies of 14 patients (mean age 33 years) with trauma to the posterolateral aspect of the knee were retrospectively reviewed, and the imaging findings were correlated with those of surgery.

Results: In all patients, MRI showed an intact iliotibial (ITB) band. MRI showed injury to the biceps tendon in 11 (79%), the gastrocnemius tendon in 1 (7%), the popliteus tendon in 5 (36%), and the lateral collateral ligament (LCL) in 14 (100%) patients. Tear of the anterior cruciate ligament (ACL) was seen in 11 (79%) patients and tear of the posterior cruciate ligament (PCL) in 4 (29%) patients. With routine MRI, visualization of the popliteofibular or fabellofibular ligaments was incomplete. On MRI, the lateral meniscus and the medial meniscus were torn with equal frequency ( n = 4; 29%). Osteochondral defects were seen in 5 (36%) cases and joint effusion in all 14 (100%) cases on MRI. Using surgical findings as the standard for diagnosis, MRI proved 86% accurate in the detection of injury to the ITB band, the biceps tendon (93%), the gastrocnemius tendon (100%), the popliteus tendon (86%), the LCL (100%), the ACL (79%), the PCL (86%), the lateral meniscus (90%), the medial meniscus (82%), and the osteochondral structures (79%). Surgical correlation confirmed the MRI findings of joint effusion in all cases.

Conclusion: MRI is well suited for demonstrating the presence and extent of injuries of the major structures of the posterolateral complex of the knee, allowing characterization of the severity of injury.
Does computer‐aided detection assist in the early detection of breast cancer?
Authors: Hukkinen K. , Pamilo M.
Published: December 2009

Purpose: To evaluate whether breast cancers detected at screening are visible in previous mammograms, and to assess the performance of a computer‐aided detection (CAD) system in detecting lesions in preoperative and previous mammograms.

Material and Methods: Initial screening detected 67 women with 69 surgically verified breast cancers (Group A). An experienced screening radiologist retrospectively analyzed previous mammograms for visible lesions (Group B), noting in particular their size and morphology. Preoperative and previous mammograms were analyzed with CAD; a relatively inexperienced resident also analyzed previous mammograms. The performances of CAD and resident were then compared.

Results: Of the 69 lesions identified, 36 were visible in previous mammograms. Of these 36 “missed” lesions, 14 were under 10 mm in diameter and 29 were mass lesions. The sensitivity of CAD was 81% in Group A and 64% in Group B. Small mass lesions were harder for CAD to detect. The specificity of CAD was 3% in Group A and 9% in Group B. Together, CAD and the resident found more “missed” lesions than separately.

Conclusion: Of the 69 breast cancers, 36 were visible in previous mammograms. CAD's sensitivity in detecting cancer lesions ranged from 64% to 81%, while specificity ranged from 9% to as low as 3%. CAD may be helpful if the radiologist is less subspecialized in mammography.
Placenta increta after first-trimester dilatation and curettage manifesting as an unusual uterine mass: magnetic resonance findings
Authors: Ju W. , Kim S. C.
Published: December 2009

Placenta increta during the first trimester of pregnancy is extremely rare. Only a few cases of placenta accreta during the latter half of pregnancy manifesting as a uterine mass have been published. This report describes a case of placenta increta that caused prolonged bleeding after a first-trimester abortion, and was identified by magnetic resonance imaging (MRI) as a heterogeneous mass in the myometrium. This is the first report of a placenta increta detected as a uterine mass after first-trimester dilatation and curettage, and its MRI findings.
Influence of the target vessel on the location and area of maximum skin dose during percutaneous coronary intervention
Authors: Chida K. , Fuda K. , Kagaya Y. , Saito H. , Takai Y. , Kohzuki M. , Takahashi S. , Yamada S. , Zuguchi M.
Published: December 2009

Background: A number of cases involving radiation-associated patient skin injury attributable to percutaneous coronary intervention (PCI) have been reported. Knowledge of the location and area of the patient's maximum skin dose (MSD) in PCI is necessary to reduce the risk of skin injury.

Purpose: To determine the location and area of the MSD in PCI, and separately analyze the effects of different target vessels.

Material and Methods: 197 consecutive PCI procedures were studied, and the location and area of the MSD were calculated by a skin-dose mapping software program: Caregraph. The target vessels of the PCI procedures were divided into four groups based on the American Heart Association (AHA) classification.

Results: The sites of the MSD for AHA #1–3, AHA #4, and AHA #11–15 were located mainly on the right back skin, the lower right or center back skin, and the upper back skin areas, respectively, whereas the MSD sites for the AHA #5–10 PCI were widely spread. The MSD area for the AHA #4 PCI was larger than that for the AHA #11–15 PCI ( P<0.0001).

Conclusion: Although the radiation associated with PCI can be widely spread and variable, we observed a tendency regarding the location and area of the MSD when we separately analyzed the data for different target vessels. We recommend the use of a smaller radiation field size and the elimination of overlapping fields during PCI.
Statin-treated familial hypercholesterolemia patients with coronary heart disease and pronounced atherosclerosis do not have more brain lesions than healthy controls in later middle age
Authors: Soljanlahti S. , Raininko R. , Hyttinen L. , Lauerma K. , Keto P. , Vuorio A. F. , Autti T.
Published: December 2009

Background: Clinically silent brain lesions detected with magnetic resonance imaging (MRI) are associated with increased risk for stroke, while stroke risk is controversial in familial hypercholesterolemia (FH).

Purpose: To determine whether the occurrence and size of clinically silent brain lesions in FH patients with coronary heart disease (CHD) is higher than in neurologically healthy controls without CHD.

Material and Methods: Brain MRI (1.5T) was performed on 19 DNA-test-verified FH patients with CHD and on 29 cardiovascularly and neurologically healthy controls, all aged 48 to 64 years. All patients were on cardiovascular medication. Intracranial arteries were evaluated by MR angiography. Infarcts, including lacunas, and white matter T2 hyperintensities (WMHI), considered as signs of small vessel disease, were recorded. A venous blood sample was obtained for assessment of risk factors. Carotid and femoral intima-media thicknesses (IMT), assessed with ultrasound, were indicators of overall atherosclerosis.

Results: On intracranial MR angiography, three patients showed irregular walls or narrowed lumens in intracranial carotid arteries. No silent infarcts appeared, and no differences in numbers or sizes of WMHIs between groups were recorded. Patients had greater carotid and femoral IMTs, and a greater number of carotid and femoral plaques. Cholesterol-years score, level of low-density lipoprotein (LDL) cholesterol, and level of high-sensitivity C-reactive protein (hsCRP) of the FH-North Karelia patients were higher than those of the controls, while the level of high-density lipoprotein (HDL) cholesterol in controls was higher.

Conclusion: FH patients with CHD and adequate cardiovascular risk-factor treatment showed no difference in the amount or size of clinically silent brain lesions compared to controls, despite patients' more severe atherosclerosis.
Intracranial infections: clinical and imaging characteristics
Authors: Foerster B. R. , Thurnher M. M. , Malani P. N. , Petrou M. , Carets-Zumelzu F. , Sundgren P. C.
Published: December 2009

The radiologist plays a crucial role in identifying and narrowing the differential diagnosis of intracranial infections. A thorough understanding of the intracranial compartment anatomy and characteristic imaging findings of specific pathogens, as well incorporation of the clinical information, is essential to establish correct diagnosis. Specific types of infections have certain propensities for different anatomical regions within the brain. In addition, the imaging findings must be placed in the context of the clinical setting, particularly in immunocompromised and human immunodeficiency virus (HIV)-positive patients. This paper describes and depicts infections within the different compartments of the brain. Pathology-proven infectious cases are presented in both immunocompetent and immunocompromised patients, with a discussion of the characteristic findings of each pathogen. Magnetic resonance spectroscopy (MRS) characteristics for several infections are also discussed.
A case-control study to estimate the impact of the icelandic population-based mammography screening program on breast cancer death
Authors: Gabe R. , Tryggvadóttir L. , Sigfússon B. F. , Ólafsdóttir G. H. , Sigur▒sson K. , Duffy S. W.
Published: December 2009

Background: The Icelandic breast cancer screening program, initiated November 1987 in Reykjavik and covering the whole country from December 1989, comprises biennial invitation to mammography for women aged 40–69 years old.

Purpose: To estimate the impact of mammography service screening in Iceland on deaths from breast cancer.

Material and Methods: Cases were deaths from breast cancer from 1990 onwards in women aged 40 and over at diagnosis, during the period November 1987 to December 31, 2002. Age- and screening-area-matched, population-based controls were women who had also been invited to screening but were alive at the time their case died.

Results: Using conditional logistic regression on the data from 226 cases and 902 controls, the odds ratio for the risk of death from breast cancer in those attending at least one screen compared to those never screened was 0.59 (95% CI 0.41–0.84). After adjustment for healthy-volunteer bias and screening-opportunity bias, the odds ratio was 0.65 (95% CI 0.39–1.09).

Conclusion: These results indicate a 35–40% reduction in breast cancer deaths by attending the Icelandic breast cancer screening program. These results are consistent with the overall evidence from other observational evaluations of mammography-based programs.
Net Effects
Authors: Hewitt Duncan
Published: December 2009

Duncan Hewitt reflects on a year of contradiction in China, where control and openness co-exist
Value of 3D-volume rendering in the assessment of coronary arteries with retrospectively ECG-gated multislice spiral CT
Authors: Mahnken A. H. , Wildberger J. E. , Sinha A. M. , Dedden K. , Stanzel S. , Hoffmann R. , Schmitz-Rode T. , Günther R. W.
Published: December 2009

Purpose: To assess the diagnostic value and measurement precision of 3D volume rendering technique (3D-VRT) from retrospectively ECG-gated multislice spiral CT (MSCT) data sets for imaging of the coronary arteries.

Material and Methods: In 35 patients, retrospectively ECG-gated MSCT of the heart using a four detector row MSCT scanner with a standardized examination protocol was performed as well as quantitative X-ray coronary angiography (QCA). The MSCT data was assessed on segmental basis using 3D-VRT exclusively. The coronary artery diameters were measured at the origin of each main coronary branch and 1 cm, 3 cm and 5 cm distally. The minimum, maximum and mean diameters were determined from MSCT angiography and compared to QCA.

Results: A total of 353 of 525 (67.2%) coronary artery segments were assessable by MSCT angiography. The proximal segments were more often assessable when compared to the distal segments. Stenoses were detected with a sensitivity of 82.6% and a specificity of 92.8%. According to the Bland-Altmanmethod the mean differences between QCA and MSCT ranged from −0.55 to 1.07 mm with limits of agreement from −2.2 mm to −2.7 mm.

Conclusion: When compared to QCA, the ability of 3D-VRT to quantitatively assess coronary artery diameters and coronary artery stenoses is insufficient for clinical purposes.
Lung perfusion scintigraphy prior to lung volume reduction surgery
Authors: Cederlund K. , Högberg S. , Jorfeldt L. , Larsen F. , Norman M. , Rasmussen E. , Tylén U.
Published: December 2009

Purpose: The aim of this study was to evaluate whether lung perfusion scintigraphy (LPS) contributes to the preoperative classification of emphysema heterogeneity in patients undergoing LVRS (lung volume reduction surgery) compared to classification based only on computed tomography (CT).

Material and Methods: Forty-five potential candidates for LVRS were examined with CT and LPS. The distribution of emphysema within the lungs was visually classified into three categories: markedly heterogeneous, intermediately heterogeneous, or homogeneous. The results of the two imaging techniques were compared to an objective, CT-based computerized classification of heterogeneity.

Results: Visual evaluation of all 90 lungs resulted in 50 correct classifications based on CT, in 40 based on LPS and in 68 correct classifications based on the combination of CT and LPS. The combination was superior to CT alone ( p<0.01) in classification of emphysema heterogeneity. There was no significant difference between the evaluations based on either CT or LPS.

Conclusion: The combined information from CT and LPS are superior in assessing emphysema heterogeneity prior to LVRS.
Modified carpal box technique in the diagnosis of suspected scaphoid fractures
Authors: Toth F. , Mester S. , Cseh G. , Bener A. , Nyarady J. , Lovasz G.
Published: December 2009

Purpose: To establish and test the clinical efficacy of a new diagnostic algorithm with the extensive utilization of modified carpal box radiography (mX-CB) in the detection of scaphoid fractures.

Material and Methods: Initial and early follow-up radiographic evaluation of 146 suspected scaphoid fractures were carried out by mX-CB. Patients with unconfirmed diagnosis were referred to CT. Patients were followed for 1 year after injury. Sensitivity, specificity and interobserver agreement of reading mX-CB images were determined statistically.

Results: No non-union or avascular necrosis was seen at 1 year after the injury. 90% of the fractures were diagnosed by mX-CB, only 6.8% of the patients needed referral to CT. Sensitivity of mX-CB at initial presentation was 81.6%. Interobserver agreement was very high among evaluators of mX-CB images.

Conclusion: Extensive utilization of mX-CB as primary and early follow-up investigation resulted in high initial diagnostic accuracy and low referral rate to a more expensive diagnostic modality.
Simultaneous voiding cystourethrography and voiding urosonography: Diagnostic comparison for vesicoureteral reflux
Authors: Uhl M. , Kromeier J. , Zimmerhackl L.-B. , Darge K.
Published: December 2009

Purpose: To compare the diagnostic accuracy of contrast-enhanced voiding urosonography (VUS) and voiding cystourethrography (VCUG) during simultaneous performance of both examinations.

Material and Methods: A total of 24 children, 16 girls and 8 boys, with a mean age of 3.5 years referred for reflux examination were recruited for the study. After transurethral bladder catheterization, radiographic contrast medium, followed directly by the US contrast medium, were administered. Fluoroscopic VCUG and VUS were carried out concurrently in the same patient. When 1 kidney was scanned by ultrasound, fluoroscopy was performed on the contralateral side.

Results: In 19 of the 47 kidney-ureter-units (KUU) vesicoureteral reflux (VUR) was detected. In 16 units the reflux was detected by both VCUG and VUS. In 3 KUUs the reflux was detected only at VCUG. All 3 cases were grade 1. Taking the VCUG as the reference standard, VUS had 84% sensitivity, 100% specificity, 100% and 90% positive and negative predictive values, respectively.

Conclusion: A dependable comparison could be achieved by performing VCUG and VUS at the same time and under the same conditions. It reconfirmed that VUS is reliable in the exclusion or verification of reflux.
CT pulmonary angiography and suspected acute pulmonary embolism
Authors: Enden T. , Kløw N.-E.
Published: December 2009

Purpose: To evaluate the use and quality of CT pulmonary angiography in our department, and to relate the findings to clinical parameters and diagnoses.

Material and Methods: A retrospective study of 324 consecutive patients referred to CT pulmonary angiography with clinically suspected pulmonary embolism (PE). From the medical records we registered clinical parameters, blood gases, d-dimer, risk factors and the results of other relevant imaging studies.

Results: 55 patients (17%) had PE detected on CT. 39 had bilateral PE, and 8 patients had isolated peripheral PE. 87% of the examinations showing PE had satisfactory filling of contrast material including the segmental pulmonary arteries, and 60% of the subsegmental arteries.D-dimer test was performed in 209 patients, 85% were positive. A negativeD-dimer ruled out PE detected at CT. Dyspnea and concurrent symptoms or detection of deep vein thrombosis (DVT), contraceptive pills and former venous thromboembolism (VTE) were associated with PE. The presence of only one clinical parameter indicated a negative PE diagnosis ( p < 0.017), whereas two or more suggested a positive PE diagnosis ( p < 0.002). CT also detected various ancillary findings such as consolidation, pleural effusion, nodule or tumor in nearly half of the patients; however, there was no association with the PE diagnosis.

Conclusion: The quality of CT pulmonary angiography was satisfactory as a first-line imaging of PE. CT also showed additional pathology of importance in the chest. Our study confirmed that a negativeD-dimer ruled out clinically suspected VTE.