bluuebunny/crossref_metadata_2025 huggingface dataset:
SENSE phase‐constrained magnitude reconstruction with iterative phase refinement
Authors: Lew Calvin , Pineda Angel R. , Clayton David , Spielman Dan , Chan Frandics , Bammer Roland
Published: October 2007

Conventional sensitivity encoding (SENSE) reconstruction is based on equations in the complex domain. However, for many MRI applications only the magnitude is relevant. If there exists an estimate of the underlying phase information, a magnitude‐only phase‐constrained reconstruction can help to improve the conditioning of the SENSE reconstruction problem. Consequently, this reduces g‐factor‐related noise enhancement. In previous attempts at phase‐constrained SENSE reconstruction, image quality was hampered by strong aliasing artifacts resulting from inadequate phase estimates and high sensitivity to phase errors. If a full‐resolution phase image is used, a significant reduction in aliasing errors and better noise properties compared to SENSE can be obtained. An iterative scheme that improves the phase estimate to better approximate the phase is presented. The mathematical framework of the new approach is provided together with comparisons of conventional SENSE, phase‐constrained SENSE, and the new phase‐refinement method. Both theory and experimental verification demonstrate significantly better noise performance at high reduction factors, i.e., close to the theoretical limit. For applications that need only magnitude data, an iterative phase‐constrained SENSE reconstruction can provide substantial SNR improvement over SENSE reconstruction and less artifacts than phase‐constrained SENSE. Magn Reson Med 58:910–921, 2007. © 2007 Wiley‐Liss, Inc.
k‐t2BLAST: Exploiting spatiotemporal structure in simultaneously cardiac and respiratory time‐resolved volumetric imaging
Authors: Sigfridsson Andreas , Wigström Lars , Kvitting John‐Peder Escobar , Knutsson Hans
Published: October 2007

Multidimensional imaging resolving both the cardiac and respiratory cycles simultaneously has the potential to describe important physiological interdependences between the heart and pulmonary processes. A fully five‐dimensional acquisition with three spatial and two temporal dimensions is hampered, however, by the long acquisition time and low spatial resolution. A technique is proposed to reduce the scan time substantially by extending thek‐tBLAST framework to two temporal dimensions. By sampling thek‐tspace sparsely in a lattice grid, the signal in the transform domain,x‐fspace, can be densely packed, exploiting the fact that large regions in the field of view have low temporal bandwidth. A volumetric online prospective triggering approach with full cardiac and respiratory cycle coverage was implemented. Retrospective temporal interpolation was used to refine the timing estimates for the center ofk‐space, which is sampled for all cardiac and respiratory time frames. This resulted in reduced reconstruction error compared with conventionalk‐tBLAST reconstruction. Thek‐t2BLAST technique was evaluated by decimating a fully sampled five‐dimensional data set, and feasibility was further demonstrated by performing sparsely sampled acquisitions. Compared to the fully sampled data, a fourfold improvement in spatial resolution was accomplished in approximately half the scan time. Magn Reson Med 58:922–930, 2007. © 2007 Wiley‐Liss, Inc.
Wideband SSFP: Alternating repetition time balanced steady state free precession with increased band spacing
Authors: Nayak Krishna S. , Lee Hsu‐Lei , Hargreaves Brian A. , Hu Bob S.
Published: October 2007

Balanced steady‐state free precession (SSFP) imaging is limited by off‐resonance banding artifacts, which occur with periodicity 1/TR in the frequency spectrum. A novel balanced SSFP technique for widening the band spacing in the frequency response is described. This method, called wideband SSFP, utilizes two alternating repetition times with alternating RF phase, and maintains high SNR and T2/T1 contrast. For a fixed band spacing, this method can enable improvements in spatial resolution compared to conventional SSFP. Alternatively, for a fixed readout duration this method can widen the band spacing, and potentially avoid the banding artifacts in conventional SSFP. The method is analyzed using simulations and phantom experiments, and is applied to the reduction of banding artifacts in cine cardiac imaging and high‐resolution knee imaging at 3T. Magn Reson Med 58:931–938, 2007. © 2007 Wiley‐Liss, Inc.
3He MRI in mouse models of asthma
Authors: Driehuys Bastiaan , Walker Julia , Pollaro Jim , Cofer Gary P. , Mistry Nilesh , Schwartz David , Johnson G. Allan
Published: October 2007

In the study of asthma, a vital role is played by mouse models, because knockout or transgenic methods can be used to alter disease pathways and identify therapeutic targets that affect lung function. Assessment of lung function in rodents by available methods is insensitive because these techniques lack regional specificity. A more sensitive method for evaluating lung function in human asthma patients uses hyperpolarized (HP) 3He MRI before and after bronchoconstriction induced by methacholine (MCh). We now report the ability to perform such 3He imaging of MCh response in mice, where voxels must be ∼3000 times smaller than in humans and 3He diffusion becomes an impediment to resolving the airways. We show three‐dimensional (3D) images that reveal airway structure down to the fifth branching and visualize ventilation at a resolution of 125 × 125 × 1000 μm3. Images of ovalbumin (OVA)‐sensitized mice acquired after MCh show both airway closure and ventilation loss. To also observe the MCh response in naive mice, we developed a non‐slice‐selective 2D protocol with 187 × 187 μm2 resolution that was fast enough to record the MCh response and recovery with 12‐s temporal resolution. The extension of 3He MRI to mouse models should make it a valuable translational tool in asthma research. Magn Reson Med 58:893–900, 2007. © 2007 Wiley‐Liss, Inc.
Axonal damage in the spinal cord of multiple sclerosis patients detected by magnetic resonance spectroscopy
Authors: Blamire Andrew M. , Cader Sarah , Lee Martin , Palace Jackie , Matthews Paul M.
Published: October 2007

Axonal damage is a major factor contributing to permanent disability in patients with multiple sclerosis (MS); it has been extensively investigated in the brain using magnetic resonance spectroscopy (MRS). In this study, MRS was used to investigate the degree of neuronal damage in the cervical spinal cord in MS. Spectra were acquired from spinal cord and brain in 11 patients with MS (expanded disability status score [EDSS], range 2.5–7.0) and 11 controls. Brain lesion volume and spinal cord cross‐sectional area were measured. Concentration of the neuronal metabolite N‐acetyl‐aspartate ([NAA]) was reduced in the spinal cord in MS patients relative to controls (reduced by 32%, P < 0.05), indicating significant neuronal damage. Additionally, the spinal cord was significantly atrophied in MS patients (15%, P < 0.001). No significant reduction in brain [NAA] was seen in the MS group. There were no correlations between clinical measures and cord atrophy or brain lesion volume on MRI; however, spinal cord [NAA] correlated with the cerebellar subscore of the neurological assessment (P < 0.005), while brain [NAA] correlated with disease duration (P < 0.05). MRS demonstrated cellular damage within the cord over and above the tissue atrophy seen by MRI. Combining MRI and MRS may therefore give a more complete picture of neurodegeneration in the spinal cord. Magn Reson Med 58:880–885, 2007. © 2007 Wiley‐Liss, Inc.
Optimized T1‐weighted contrast for single‐slab 3D turbo spin‐echo imaging with long echo trains: Application to whole‐brain imaging
Authors: Park Jaeseok , Mugler John P. , Horger Wilhelm , Kiefer Berthold
Published: October 2007

T1‐weighted contrast is conventionally obtained using multislice two‐dimensional (2D) spin‐echo (SE) imaging. Achieving isotropic, high spatial resolution is problematic with conventional methods due to a long acquisition time, imperfect slice profiles, or high‐energy deposition. Single‐slab 3D SE imaging was recently developed employing long echo trains with variable low flip angles to address these problems. However, long echo trains may yield suboptimal T1‐weighted contrast, since T2 weighting of the signals tends to develop along the echo train. Image blurring may also occur if high spatial frequency signals are acquired with low signal intensity. The purpose of this work was to develop an optimized T1‐weighted version of single‐slab 3D SE imaging with long echo trains. Refocusing flip angles were calculated based on a tissue‐specific prescribed signal evolution. Spatially nonselective excitation was used, followed by half‐Fourier acquisition in the in‐plane phase encoding (PE) direction. Restore radio frequency (RF) pulses were applied at the end of the echo train to optimize T1‐weighted contrast. Imaging parameters were optimized by using Bloch equation simulation, and imaging studies of healthy subjects were performed to investigate the feasibility of whole‐brain imaging with isotropic, high spatial resolution. The proposed technique permitted highly‐efficient T1‐weighted 3D SE imaging of the brain. Magn Reson Med 58:982–992, 2007. © 2007 Wiley‐Liss, Inc.
Tracer kinetic model–driven registration for dynamic contrast‐enhanced MRI time‐series data
Authors: Buonaccorsi Giovanni A. , O'Connor James P.B. , Caunce Angela , Roberts Caleb , Cheung Sue , Watson Yvonne , Davies Karen , Hope Lynn , Jackson Alan , Jayson Gordon C. , Parker Geoffrey J.M.
Published: October 2007

Dynamic contrast‐enhanced MRI (DCE‐MRI) time series data are subject to unavoidable physiological motion during acquisition (e.g., due to breathing) and this motion causes significant errors when fitting tracer kinetic models to the data, particularly with voxel‐by‐voxel fitting approaches. Motion correction is problematic, as contrast enhancement introduces new features into postcontrast images and conventional registration similarity measures cannot fully account for the increased image information content. A methodology is presented for tracer kinetic model–driven registration that addresses these problems by explicitly including a model of contrast enhancement in the registration process. The iterative registration procedure is focused on a tumor volume of interest (VOI), employing a three‐dimensional (3D) translational transformation that follows only tumor motion. The implementation accurately removes motion corruption in a DCE‐MRI software phantom and it is able to reduce model fitting errors and improve localization in 3D parameter maps in patient data sets that were selected for significant motion problems. Sufficient improvement was observed in the modeling results to salvage clinical trial DCE‐MRI data sets that would otherwise have to be rejected due to motion corruption. Magn Reson Med 58:1010–1019, 2007. © 2007 Wiley‐Liss, Inc.
Refining the sensory and motor ratunculus of the rat upper extremity using fMRI and direct nerve stimulation
Authors: Cho Younghoon R. , Pawela Christopher P. , Li Rupeng , Kao Dennis , Schulte Marie L. , Runquist Matthew L. , Yan Ji‐Geng , Matloub Hani S. , Jaradeh Safwan S. , Hudetz Anthony G. , Hyde James S.
Published: October 2007

It is well understood that the different regions of the body have cortical representations in proportion to the degree of innervation. Our current understanding of the rat upper extremity has been enhanced using functional MRI (fMRI), but these studies are often limited to the rat forepaw. The purpose of this study is to describe a new technique that allows us to refine the sensory and motor representations in the cerebral cortex by surgically implanting electrodes on the major nerves of the rat upper extremity and providing direct electrical nerve stimulation while acquiring fMRI images. This technique was used to stimulate the ulnar, median, radial, and musculocutaneous nerves in the rat upper extremity using four different stimulation sequences that varied in frequency (5 Hz vs. 10 Hz) and current (0.5 mA vs. 1.0 mA). A distinct pattern of cortical activation was found for each nerve. The higher stimulation current resulted in a dramatic increase in the level of cortical activation. The higher stimulation frequency resulted in both increases and attenuation of cortical activation in different regions of the brain, depending on which nerve was stimulated. Magn Reson Med 58:901–909, 2007. © 2007 Wiley‐Liss, Inc.
Three‐dimensional J‐resolved H‐1 magnetic resonance spectroscopic imaging of volunteers and patients with brain tumors at 3T
Authors: Li Yan , Chen Albert P. , Crane Jason C. , Chang Susan M. , Vigneron Daniel B. , Nelson Sarah J.
Published: October 2007

A method that combines two‐dimensional (2D) J‐resolved spectroscopy with three spatial dimension magnetic resonance spectroscopic imaging (MRSI) is introduced to measure J‐coupled metabolites of glutamate (Glu), glutamine (Gln), myo‐Inositol (mI), and lactate (Lac) in the brain and to simultaneously obtain T2 values of choline (Cho), creatine (Cr), and N‐acetyl aspartate (NAA). Relatively few points in the t1 dimension (six echo times) and a flyback echo‐planar trajectory were incorporated in the acquisition to speed up the total acquisition time so that it was within a clinically feasible range (23 min). Data obtained using GAMMA software simulations and from phantoms have shown that the 4CH2 resonances of Glu can be separated from Gln at 2.35 ppm in TE‐averaged spectra. Results from phantoms, six normal volunteers, and four patients demonstrated good signal‐to‐noise ratio (SNR). The J cross‐peaks from the methyl group of Lac were visualized in the 2D spectra from the phantom and the glioma patient, and could be quantified from the spectra at J = ±4.17 Hz. This technique also enables the evaluation of the changes in metabolite T2. Compared with the values in normal white matter, the T2 values of Cho and Cr were statistically significantly increased in regions of glioma. Magn Reson Med 58:886–892, 2007. © 2007 Wiley‐Liss, Inc.
Quantitative cerebral perfusion using dynamic susceptibility contrast MRI: Evaluation of reproducibility and age‐ and gender‐dependence with fully automatic image postprocessing algorithm
Authors: Shin Wanyong , Horowitz Sandra , Ragin Ann , Chen Yufen , Walker Matthew , Carroll Timothy J.
Published: October 2007

A novel approach for quantifying cerebral blood flow (CBF) is proposed that combines the bookend technique of calculating cerebral perfusion with an automatic postprocessing algorithm. The reproducibility of the quantitative CBF (qCBF) measurement in healthy controls (N = 8) showed a higher intraclass correlation coefficient (ICC) and lower coefficient of variation (COV) when calculated with automatic analysis (ICC/COV = 0.90/0.09) than when compared to conventional manual analysis (ICC/COV = 0.58/0.19). Also, the reproducibility in patients (N = 25) was successfully evaluated with the automatic analysis (ICC/COV = 0.81/0.14). In 175 consecutive clinical scans, we found 3.0% and 7.4% of qCBF decrease per decade in white matter (WM) (21.5 ± 6.66 ml/100 g‐min) and gray matter (GM) (49.6 ± 16.2 ml/100 g‐min), respectively. Cerebral blood volume (CBV) showed a significant 3.7% decrease per decade in GM (3.00 ± 0.94 ml/100 g) but not in WM (1.69 ± 0.40 ml/100 g). Mean transit time (MTT) increased by 1.9% and 3.8% per decade in WM (5.04 ± 0.88 s) and GM (4.14 ± 0.80 s), respectively. qCBF and MTT values between males (N = 85) and females (N = 90) were significantly different in GM. Women showed 11% higher qCBF as well as a higher decrease in qCBF with increasing age than men in the whole brain (WB). Our results supported the notion that population average empirical quantification of cerebral perfusion is subject to individual variation as well as age‐ and gender‐dependent variability. Magn Reson Med, 2007. © 2007 Wiley‐Liss, Inc.
Non‐Cartesian data reconstruction using GRAPPA operator gridding (GROG)
Authors: Seiberlich Nicole , Breuer Felix A. , Blaimer Martin , Barkauskas Kestutis , Jakob Peter M. , Griswold Mark A.
Published: October 2007

A novel approach that uses the concepts of parallel imaging to grid data sampled along a non‐Cartesian trajectory using GRAPPA operator gridding (GROG) is described. GROG shifts any acquired data point to its nearest Cartesian location, thereby converting non‐Cartesian to Cartesian data. Unlike other parallel imaging methods, GROG synthesizes the net weight for a shift in any direction from a single basis set of weights along the logical k‐space directions. Given the vastly reduced size of the basis set, GROG calibration and reconstruction requires fewer operations and less calibration data than other parallel imaging methods for gridding. Instead of calculating and applying a density compensation function (DCF), GROG requires only local averaging, as the reconstructed points fall upon the Cartesian grid. Simulations are performed to demonstrate that the root mean square error (RMSE) values of images gridded with GROG are similar to those for images gridded using the gold‐standard convolution gridding. Finally, GROG is compared to the convolution gridding technique using data sampled along radial, spiral, rosette, and BLADE (a.k.a. periodically rotated overlapping parallel lines with enhanced reconstruction [PROPELLER]) trajectories. Magn Reson Med, 2007. © 2007 Wiley‐Liss, Inc.
Distance‐two interpolation for parallel algebraic multigrid
Authors: De Sterck Hans , Falgout Robert D. , Nolting Joshua W. , Yang Ulrike Meier
Published: October 2007

Algebraic multigrid (AMG) is one of the most efficient and scalable parallel algorithms for solving sparse linear systems on unstructured grids. However, for large 3D problems, the coarse grids that are normally used in AMG often lead to growing complexity in terms of memory use and execution time per AMG V‐cycle. Sparser coarse grids, such as those obtained by the parallel modified independent set (PMIS) coarsening algorithm, remedy this complexity growth but lead to nonscalable AMG convergence factors when traditional distance‐one interpolation methods are used. In this paper, we study the scalability of AMG methods that combine PMIS coarse grids with long‐distance interpolation methods. AMG performance and scalability are compared for previously introduced interpolation methods as well as new variants of them for a variety of relevant test problems on parallel computers. It is shown that the increased interpolation accuracy largely restores the scalability of AMG convergence factors for PMIS‐coarsened grids, and in combination with complexity reducing methods, such as interpolation truncation, one obtains a class of parallel AMG methods that enjoy excellent scalability properties on large parallel computers. Copyright © 2007 John Wiley & Sons, Ltd.
Fetal cardiac stroke volume determination by four‐dimensional ultrasound with spatio‐temporal image correlation compared with two‐dimensional and Doppler ultrasonography
Authors: Rizzo Giuseppe , Capponi Alessandra , Cavicchioni Ottavia , Vendola Marianne , Arduini Domenico
Published: October 2007

Objective

To assess the agreement of stroke volume (SV) measured with two‐dimensional (2D) ultrasonography with Doppler capability (vs) four‐dimensional (4D) with spatiotemporal image correlation (STIC) in normal and growth restricted fetuses.

Methods

2D Doppler and 4D STIC were used to measure SV of 40 normal fetuses at 20 to 22 and 28 to 32 weeks, and 16 growth‐restricted fetuses at 26 to 34 weeks of gestation. Intraclass correlation was used to evaluate the agreement between left and right SV obtained by the two techniques, and proportionate Bland–Altman plots constructed. The time necessary to obtain SV was analyzed.

Results

The intraclass correlation coefficient between 2D Doppler and 4D STIC measurements for the left ventricle were 0.977 and 0.980 for the right ventricle. The proportionate limits of agreement between the two methods were 18.7 to 23.9% for the left ventricle and − 20.9 to 21.7% for the right ventricle. The time necessary to measure SV was significantly shorter with 4D STIC (3.1 (vs) 7.9 min p < 0.0001) than with 2D Doppler.

Conclusions

There is a good agreement between SV measured either by 2D Doppler or by 4D STIC. The 4D STIC represents a simple and rapid technique to estimate fetal SV and promises to become the method of choice. Copyright © 2007 John Wiley & Sons, Ltd.
Maternal urine for prenatal diagnosis—an analysis of cell‐free fetal DNA in maternal urine and plasma in the third trimester
Authors: Majer Sandra , Bauer Margit , Magnet Eva , Strele Andrea , Giegerl Elisabeth , Eder Martina , Lang Uwe , Pertl Barbara
Published: October 2007

Objectives

The aim of the study was the detection, quantification and correlation of cell‐free fetal (cff) DNA in maternal urine and plasma in normal and complicated pregnancies during the third trimester.

Methods

One hundred and fifty‐one urine and plasma samples obtained from 96 women carrying male fetuses, and 55 carrying female fetuses were collected and analyzed for cff‐DNA using fluorescent PCR and quantitative real‐time PCR. DNA was extracted from 1 mL maternal urine and analyzed with two different primer sets (SRY and DYS‐14). The concentrations of cff and total DNA in maternal plasma were correlated with maternal and obstetric parameters using appropriate correlation analyses.

Results

Y‐chromosome‐specific sequences were detected in 31 of 96 (32.3%) urine samples collected from women pregnant with male fetuses using DYS‐14 and in 6 of 96 (6.3%) urine samples using SRY as primers using real‐time PCR. All 96 plasma samples obtained from women carrying male fetuses were positive for cff‐DNA using real‐time PCR. Cff‐DNA exhibited a correlation with gestational age (R = 0.244; P = 0.018) and an inverse correlation with the latency between blood collection and birth (R = − 0.218; P = 0.036). Total DNA showed a correlation with placental weight (R = 0.182; P = 0.034) and pregnancy‐associated complications (R = 0.280; P < 0.001).

Conclusion

Our data confirm that cff‐DNA is cleared by the kidneys in detectable amounts, but due to its low concentration or problematic detection in maternal urine this source seems inappropriate for noninvasive prenatal diagnosis. Copyright © 2007 John Wiley & Sons, Ltd.
Controlling numbers and sizes of beads in electrospun nanofibers
Authors: Liu Yong , He Ji‐Huan , Yu Jian‐yong , Zeng Hong‐mei
Published: October 2007

BACKGROUND: Electrospinning is a powerful and effective method to produce nanofibers. Beads have been observed widely in electrospun products, but effects of solvents, weight concentrations and salt additives on the number and morphology of beads in the electrospinning process have not been systematically studied.

RESULTS: Both theoretical analysis and experimental results show that beads strongly depend upon solvents, weight concentrations and salt additives. Either a suitable weight concentration or a suitable salt additive can completely prevent the occurrence of beads in the electrospinning process; solvents can affect the number of beads and the morphology of electrospun fibers.

CONCLUSION: Beads are mainly caused by lower surface tension. With a higher surface tension, the size and number of beads in electrospun products are smaller and fewer, respectively. Copyright © 2007 Society of Chemical Industry
Identification of putative serum glycoprotein biomarkers for human lung adenocarcinoma by multilectin affinity chromatography and LC‐MS/MS
Authors: Heo Sun‐Hee , Lee Seung‐Jin , Ryoo Hyun‐Mo , Park Jae‐Yong , Cho Je‐Yoel
Published: October 2007

Glycoproteins in human serum play fundamental roles in many biological processes, and also have clinical value as biomarkers for disease progression and treatment. In this study, we isolated glycoproteins from the sera of three healthy individuals and three lung adenocarcinoma patients using multilectin affinity chromatography. The recovered glycoproteins were subjected to treatment with peptide‐N‐glycosidase F (PNGase F) and in‐gel digestion by trypsin. Tryptic peptides were analyzed by nano‐LC coupled to ESI‐MS/MS and the MS/MS spectra were processed by Bioworks 3.2 and an in‐house bioinformatics tool, ProtAn. Approximately 90% of the proteins identified contained more than one potential glycosylation site. Comparison of the serum glycoproteome of healthy and adenocarcinoma individuals revealed 38 cancer‐selective proteins. Among them, 60% have previously been reported as low abundance proteins in human sera. We identified several cancer‐selective proteins that have been previously characterized as potential indicators of lung cancer in serum or plasma, including haptoglobin (HP), inter‐α‐trypsin inhibitor heavy chain 4 (ITI‐H4), complement C3 precursor, and leucine‐rich α‐2‐glycoprotein. In addition, plasma kallikrein (KLKB1) and inter‐α‐trypsin inhibitor heavy chain 3 (ITI‐H3) were identified as being potentially elevated in the lung cancer group, and were validated by Western blot analysis. Furthermore, ∼18 kDa plasma kallirein protein fragment was detected at high levels in 25 out of 28 adenocarcinoma patients, while one of the eight normal individuals showed moderate positive. The results suggest that KLKB1 represents a potential candidate serum biomarker of lung cancer.
Cystic fibrosis in India
Authors: Kabra S.K. , Kabra M. , Lodha R. , Shastri S.
Published: October 2007

Cystic fibrosis (CF) was considered to be non‐existent in Indian subcontinent. Reports in last one decade have suggested that cystic fibrosis occurs in India but its precise magnitude is not known. Studies on migrant Indian population in United States and United Kingdom estimate frequency of CF as 1:10,000 to 1:40,000. The clinical features are similar to that reported in Caucasian population. CF in Indian children is usually diagnosed late and in advanced stage. Children are more malnourished and may have clinically evident deficiency of fat soluble vitamins. The frequency of clubbing, colonization with Pseudomonas, and laboratory evidence of pseudo‐Bartter syndrome is relatively more at the time of diagnosis. Diagnostic facilities in form of sweat chloride estimation and genetic studies are not available readily. Mutation profile is different. The frequency of common mutation F508del in Indian children is between 19% and 34%. Other mutations are heterogeneous. Management of CF in India is difficult due to less number of trained manpower, limited availability, and high cost of pharmacologic agents. The determinants of early death include: severe malnutrition and colonization with Pseudomonas at the time of diagnosis, more than four episodes of lower respiratory infection per year and age of onset of symptoms before 2 months of age. To conclude, CF does occur in India; however, precise magnitude of problem is not known. There is need to create awareness amongst pediatricians, developing diagnostic facilities, and management protocols based on locally available resources. Pediatr Pulmonol. 2007; 42:1087–1094. © 2007 Wiley‐Liss, Inc.
Partial splenectomy for portal hypertension in cystic fibrosis related liver disease
Authors: Louis Dominique , Duc Mai Linh Pham , Reix Philippe , Chazalette Jean‐Pierre , Durieu Isabelle , Feigelson Jean , Bellon Gabriel
Published: October 2007

Aims

To review the middle‐ and long‐term effects of partial splenectomy (PS) on portal hypertension (PHT) and its complications in patients with cystic fibrosis (CF) related liver disease risky PHT.

Method

Over a 20 years period, 19 patients aged 7–23 years underwent partial PS for massive splenomegaly, hypersplenism, and / or severe PHT.

Results

In all but three cases, PHT and hypersplenism have improved for long periods. Noticeable improvement of hepatic tests occurred simultaneously. In all patients PS resolved abdominal discomfort. Fifteen patients are alive and a stabilization of the liver disease occurred with a follow‐up of 1–20 years (mean 7.9). One patient died following respiratory insufficiency 10 years after PS although PHT was stable. Manifestations recurred in 2 patients 5 and 6 years after PS. In two patients, the course of the disease evolved to hepatic insufficiency without recurrence of PHT 3 and 8 years after PS. PS did not give the expected results in three cases only, in which PHT was not modified or reoccurred during the following year. No severe complication was observed. Early (three patients) or late (one patient) eventration required surgical procedure.

Conclusions

Our results show that PS is a reliable and well‐tolerated technique. Therefore, it is a therapeutic option for the management of PHT in CF patients with a preserved liver function. It can prevent and significantly delay a liver transplantation and its constraints. Pediatr Pulmonol. 2007; 42:1173–1180. © 2007 Wiley‐Liss, Inc.
Controlled‐ventilation volumetric CT scan in the evaluation of acquired pulmonary lobar emphysema: A case report
Authors: Khan Salman , Kurland Geoffrey , Newman Beverley
Published: October 2007

Acquired lobar emphysema (ALE), a clinical entity often associated with bronchopulmonary dysplasia (BPD) in premature infants, carries significant morbidity and mortality. Because of compression of adjacent lung tissue and poor response to medical therapy, patients may require surgical resection of the hyperinflated region of lung. The decision of proceed to surgery is often problematic, relying upon standard chest radiographs, ventilation‐perfusion scans, and high resolution CT (HRCT) scans. We report the use of controlled volume HRCT with breath‐holding at TLC and FRC in an infant with severe BPD and ALE. Using reconstruction software, we could estimate total lung volume as well as the volume of the lobe affected by ALE at both lung volumes, permitting the determination of the degree of air trapping. This is turn afforded us confirmatory data of the extent of the affected lung, justifying surgical removal. Pediatr Pulmonol. 2007;42:1222–1228. © 2007 Wiley‐Liss, Inc.
Superfocusing of optical beams below the diffraction limit by media with negative refraction
Authors: Husakou A. , Herrmann J.
Published: October 2007

Usual optical elements cannot focus a light beam to a spot with diameter smaller than half of the wavelength of the light; however overcoming this limit is of great importance in several high‐tech applications such as optical lithography, magneto‐optical data storage, and numerous other fields of science and industry. Here we show that it is possible to focus light to spots below the diffraction limit (superfocusing) by the combination of two main elements: one which creates weak near‐field evanescent components of the beam, and one which amplifies these evanescent fields, such as a slab of a photonic crystal with negative refraction. For the creation of seed evanescent components a wavelength‐scale aperture can be used. For superfocusing of scanning beams a light‐controlled saturable absorber or a nonlinear material with a Kerr‐type nonlinearity enables focusing of beams without spatial near‐field control to spots in the range of 0.2λ. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Preparation and application of functionalized photonic crystal fibres
Authors: Bartelt H. , Kirchhof J. , Kobelke J. , Schuster K. , Schwuchow A. , Mörl K. , Röpke U. , Leppert J. , Lehmann H. , Smolka S. , Barth M. , Benson O. , Taccheo S. , D'Andrea C.
Published: October 2007

The concept of microstructured and photonic band gap fibres opens a wide range of flexibility to introduce specific functionality in fibre light guiding properties and to adapt optical fibres to specific applications. In addition to flexible structural parameters, the use of specific material properties further increases the design freedom in optical fibres. In order to demonstrate the wide functional capabilities of such fibres, we have investigated different index guiding and photonic band gap fibres made from pure and modified silica and from non‐silica materials. The main interest in the use of different materials than the well‐known high‐purity silica is to utilize special optical properties such as high nonlinearity, specific dispersion or extended infrared transmission windows. A main challenge for such unconventional materials is to transfer the excellent properties of silica‐based photonic crystal fibres, like low spectral loss or good durability, to the modified or non‐silica materials. The preparation of modified silica‐based photonic crystal fibres was implemented by the MCVD doping process or by the use of high‐melting lanthanium or lead silicate special glasses. Highly germanium‐doped silica rods were used for the preparation of index guiding and for band gap guiding fibres. The prepared fibres were investigated in their mode propagation properties and compared to model calculations. Application examples are presented for spectral fibre sensing and for supercontinuum generation. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical properties of disordered metallic photonic crystal slabs
Authors: Nau D. , Schönhardt A. , Christ A. , Zentgraf T. , Bauer Ch. , Kuhl J. , Giessen H.
Published: October 2007

We give an overview about the optical properties of disordered metallic photonic crystal slabs. Different disorder models with different next‐neighbor correlations are artificially introduced into the samples, and their influence on the samples' transmission and bandstructure are examined. We found that uncorrelated disorder reduces the amplitude of spectral features and the width of the stop‐bands in the bandstructure. Correlated disorder additionally excites multiple resonances, resulting in broadened resonances and a destroyed bandstructure even at moderate disorder. Numerical results are presented that allow to fully interpret the experimental observations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Negative permeability around 630 nm in nanofabricated vertical meander metamaterials
Authors: Schweizer Heinz , Fu Liwei , Gräbeldinger Hedwig , Guo Hongcang , Liu Na , Kaiser Stefan , Giessen Harald
Published: October 2007

We demonstrate a new design of a 3‐dimensional meander structure that exhibits negative permeability with a broad bandwidth between 550 nm and 665 nm. The structural design allows for full coupling of the magnetic field component at all angles of incidence. We compare our structure with other metamaterial structures with respect to the series capacitance contributions of the different metamaterials. The investigation of optical metamaterials is carried out combining transmission line analysis with numerical simulations of Maxwell's equations. The analysis is demonstrated for typical split ring structures and the novel 3D meander metamaterial structures. Comparing the resulting scattering parameter spectra as well as the retrieved effective material parameters, we find that transmission line description remains valid for metamaterials at optical frequencies. We find in addition that the longitudinal capacitance is the decisive parameter to achieve negative permeability with a broad bandwidth at optical frequencies. For experimental verification we manufactured split‐ring resonator structures and meander metamaterial structures with linewidths down to 30 nm, element sizes down to 100 nm, and periods between 200 nm and 350 nm. For meander metamaterial structures a permeability value of –1 was achieved within a bandwidth of 50 nm centered at 630 nm. The largest absolute value of –4.5 was achieved at 650 nm. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigations on the generation of photonic crystals using two‐photon polymerization (2PP) of inorganic–organic hybrid polymers with ultra‐short laser pulses
Authors: Houbertz R. , Declerck P. , Passinger S. , Ovsianikov A. , Serbin J. , Chichkov B. N.
Published: October 2007

Optical devices with micro‐ and nanooptical elements using polymers and, in particular nano‐scaled organic–inorganic hybrid materials such as ORMOCER®s, will be beyond of the next generation of optical components. For the generation of photonic elements, 3D photonic bandgap materials have been proposed as the basis of many devices. In order to create complete 3D photonic bandgaps, materials enabling high refractive index contrast are needed. Combining suitable materials with highly sophisticated processing methods such as two‐photon polymerization (2PP) using femtosecond lasers is a step towards novel photonic elements. The materials and the patterning process will be discussed with respect these applications. In order to demonstrate the potential of the 2PP method, different classes of materials are investigated. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical properties of photonic/plasmonic structures in nanocomposite glass
Authors: Graener H. , Abdolvand A. , Wackerow S. , Kiriyenko O. , Hergert W.
Published: October 2007

Glass containing metallic nanoparticles shows unique optical properties and is therefore a promising material for various photonic applications. It is demonstrated, how such material can be structured using external electric fields. The optical properties of such photonic structures are investigated. Prior to the theoretical design of photonic structures in such a glass a critical investigation of the dielectric properties is necessary. A comparison of the effective medium theory and finite element calculations is given. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Polymer based tuneable photonic crystals
Authors: Wülbern J. H. , Schmidt M. , Hübner U. , Boucher R. , Volksen W. , Lu Y. , Zentel R. , Eich M.
Published: October 2007

We report on the fabrication and characterization of photonic crystal slab waveguide resonators which contain a nanostructured second‐order nonlinear optical polymer. The combination of a photonic crystal resonator realized in a second‐order nonlinear optical polymer allowed the detection of electro‐optical modulation of light with a sub‐1‐V sensitivity. Furthermore we report on the synthesis of novel nonlinear optical polymers with large second‐order hyperpolarizability and improved glass transition temperature. The polymer slab waveguide is micro patterned by means of electron‐beam lithography and reactive ion etching. The photonic crystal slab‐based resonator consisted of a square lattice of holes carrying a linear defect. Applying an external electric modulation voltage to electrodes leads to a linear electro‐optical shift of the resonance spectrum and thus to a modulation of the transmission at a fixed wavelength based on the electronic displacement polarization in a noncentrosymmetric medium (Pockels effect). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Automated interface for hyphenation of planar chromatography with mass spectrometry
Authors: Luftmann Heinrich , Aranda Mario , Morlock Gertrud E.
Published: October 2007

A fully automated interface to couple high‐performance thin‐layer chromatography (HPTLC) with mass spectrometry (MS) is described. This universal hands‐free interface connects intact normal‐phase plates to any liquid chromatography/mass spectrometry (LC/MS) system without any adjustments or modifications to the mass spectrometer. The interface extracts the complete substance band with its depth profile and thus allows detections in the pg/band range. The high performance of the automated interface was evaluated through caffeine quantification in real samples, viz., energy drinks and pharmaceutical tablets, without internal standard. Following chromatographic separation on silica gel 60 F254 HPTLC plates, caffeine bands were eluted from the plate by means of the automated interface to the electrospray ionization (ESI) source of a triple‐quadrupole mass spectrometer. Since in full scan mode only the protonated molecule [M+H]+ was observed, caffeine quantification was performed using the selected‐ion monitoring (SIM) mode at m/z 195. The validation showed highly reliable results for the linear range (R2 = 0.9973), repeatability (RSD = 5.6%, n = 6) and intermediate precision (RSD = 1.5%, n = 3). Regarding accuracy the results obtained by HPTLC/MS were not statistically different (F‐test, t‐test) from those obtained by validated HPTLC/UV methods. Hence, this interface proved to be one of the most reliable and universal interfaces for HPTLC/MS. Copyright © 2007 John Wiley & Sons, Ltd.
Fight or flight: managing stigma in executive careers
Authors: Semadeni Matthew , Cannella Jr. Albert A. , Fraser Donald R. , Lee D. Scott
Published: October 2007

We examine the labor market consequences borne by executives who remain at financially distressed firms relative to those who flee to another employer to avoid the stigma of failure. Our study makes two contributions. First, we document an ex ante dimension of executive labor markets unaccounted for by ex post settling up models. Specifically, we show that executives who ‘jump ship’—change employers in the two years prior to the failure—suffer fewer labor market consequences than their counterparts who remain with the failing firm. Second, we extend the study of bankruptcy stigma to examine how stigma might be managed by jumping ship. Copyright © 2007 John Wiley & Sons, Ltd.
Size‐Dependent Cytotoxicity of Gold Nanoparticles
Authors: Pan Yu , Neuss Sabine , Leifert Annika , Fischler Monika , Wen Fei , Simon Ulrich , Schmid Günter , Brandau Wolfgang , Jahnen‐Dechent Willi
Published: October 2007

Gold nanoparticles are widely used in biomedical imaging and diagnostic tests. Based on their established use in the laboratory and the chemical stability of Au0, gold nanoparticles were expected to be safe. The recent literature, however, contains conflicting data regarding the cytotoxicity of gold nanoparticles. Against this background a systematic study of water‐soluble gold nanoparticles stabilized by triphenylphosphine derivatives ranging in size from 0.8 to 15 nm is made. The cytotoxicity of these particles in four cell lines representing major functional cell types with barrier and phagocyte function are tested. Connective tissue fibroblasts, epithelial cells, macrophages, and melanoma cells prove most sensitive to gold particles 1.4 nm in size, which results in IC50 values ranging from 30 to 56 μM depending on the particular 1.4‐nm Au compound–cell line combination. In contrast, gold particles 15 nm in size and Tauredon (gold thiomalate) are nontoxic at up to 60‐fold and 100‐fold higher concentrations, respectively. The cellular response is size dependent, in that 1.4‐nm particles cause predominantly rapid cell death by necrosis within 12 h while closely related particles 1.2 nm in diameter effect predominantly programmed cell death by apoptosis.
The New λ6Si‐Silicate Dianion [Si(NCO)6]2−: Synthesis and Structural Characterization of [K(18‐crown‐6)]2[Si(NCO)6]
Authors: Seiler Oliver , Burschka Christian , Götz Kathrin , Kaupp Martin , Metz Stefan , Tacke Reinhold
Published: October 2007

The λ6Si‐silicate [K(18‐crown‐6)]2[Si(NCO)6] (10) was synthesized by treatment of Si(NCO)4 with KNCO in the presence of 18‐crown‐6. Compound 10 (SiN6 skeleton) is the first example of a hexa(cyanato‐N)silicate. It was characterized by solid‐state and solution NMR spectroscopy, and the acetonitrile solvate 10·2CH3CN was studied by single‐crystal X‐ray diffraction. To differentiate between the two isomeric [Si(NCO)6]2− and [Si(OCN)6]2− dianions, computational studies were performed.
Synthesis and Structures of SrAuIn and SrAuIn3
Authors: Muts Ihor R. , Pöttgen Rainer , Zaremba Vasyl I.
Published: October 2007

The intermetallic compounds SrAuIn and SrAuIn3 were synthesised from the elements in sealed tantalum ampoules in a high‐frequency furnace. Both indides were studied by X‐ray powder and single crystal diffraction: TiNiSi type, Pnma, a = 772.2(4), b = 478.6(2), c = 844.0(4) pm, wR2 = 0.0474, 748 F2 values, 20 variables for SrAuIn and BaNiSn3 type, I4mm, a = 456.97(8), c = 1243.7(3) pm, wR2 = 0.0381, 397 F2 values, 18 variables for SrAuIn3. The latter reveals a small degree of Au/In disorder. Both structures consist of three‐dimensional [AuIn], respectively [AuIn3] polyanionic networks with short Au–In distances (287–291 pm in SrAuIn and 268–284 pm in SrAuIn3. The latter indide reveals also In–In bonding (294–323 pm). The larger voids within the polyanionic networks of both structures are filled by the strontium cations.
Attempted Abstraction of the Halogenides in (HNEt3)[Re(CH3CN)2Cl4] and Crystal Structures of cis‐[Re(CH3CN)2Cl4]·CH3CN and cis‐[Re(NHC(OCH3)CH3)2Cl4]
Authors: Kunz Peter C. , Kurz Philipp , Spingler Bernhard , Alberto Roger
Published: October 2007

The abstraction of the halogenide ligands in [Re(CH3CN)2Cl4]− should result in a solvent‐only stabilized ReIII complex. The reactions of salts of [Re(CH3CN)2Cl4]− with silver(I) and thallium(I) salts were investigated and the solid‐state structures of cis‐[Re(CH3CN)2Cl4]·CH3CN and cis‐[Re(NHC(OCH3)CH3)2Cl4] are described.
5,5′‐Hydrazinebistetrazole: An Oxidation‐stable Nitrogen‐rich Compound and Starting Material for the Synthesis of 5,5′‐Azobistetrazolates
Authors: Klapötke Thomas M. , Sabaté Carles Miró
Published: October 2007

All 5,5′‐hydrazinebistetrazoles reported in the literature are sensitive to oxidation and react with atmospheric oxygen to yield the corresponding 5,5′‐azobistetrazolates on time. Herewith, we report on the synthesis of the free acid 5,5′‐hydrazinebistetrazole (HBT) which showed to be stable on air for extended periods of time. The compound was fully characterized by analytical and spectroscopic methods and its X‐ray structure was determined by diffraction techniques. Besides, we determined its explosive properties by BAM methods and calculated its heat of formation (+414 kJ mol−1), detonation velocity (8523 m s−1) and detonation pressure (27.7 GPa). HBT proved to be very safe to handle (impact sensitivity: >30 J, friction sensitivity: ∼108 N) and was used as a starting material for the synthesis of some already reported 5,5′‐azobistetrazolates: NH4+, NH2NH3+, Li+, Na+, K+, Rb+, Cs+, Mg2+, Ca2+, Sr2+ and Ba2+.
$^{1}_{\infty}\rm [Ho_{2}Cl_{6}\{1,3-Ph(CN)_{2}\}_{3}]$ – Eine zu Doppelsträngen kondensierte Variante der PaCl5‐Struktur in einem Selten‐Erd‐Benzodinitril‐Koordinationspolymer
Authors: Höller Christoph J. , Müller‐Buschbaum Klaus
Published: October 2007

$^{1}_{\infty}\rm [Ho_{2}Cl_{6}\{1,3-Ph(CN)_{2}\}_{3}]$ – A Variant of the PaCl5 Structure Condensed to Double Strands in a Rare Earth Benzodinitrile Coordination Polymer

Single crystalline transparent pink $^{1}_{\infty}\rm [Ho_{2}Cl_{6}\{1,3-Ph(CN)_{2}\}_{3}]$ (1,3‐Ph(CN)2 = 1,3‐benzodinitrile, C6H4(CN)2) was obtained by the reaction of anhydrous holmium trichloride with a melt of 1,3‐benzodinitrile at 175 °C. The trichloride structure is broken up by the dinitrile ligands and re‐arranged to double strands of edge connected pentagonal bipyramids of chlorine and nitrogen atoms. The structure can be deduced from the PaCl5 structure type by condensation of two PaCl5 strands and exchange of two chlorine atoms with nitrile groups. The double strands exhibit ligand free cavities of 600–800 pm diameter.
The X‐ray Single Crystal Structures of an Acid‐functionalized Bis(2‐picolyl)amine (bpa) Ligand with Palladium(II) and Zinc(II) Display Different Intermoleclar Interactions around the Common (H2O)2(anion)2 Motif
Authors: Kirin Srećko I. , Weyhermüller Thomas , Merz Klaus , Metzler‐Nolte Nils
Published: October 2007

This work reports structural investigations on two metal complexes of the functionalized (p‐carboxylatobenzyl)‐bis(2‐picolyl)amine ligand 1 (HL). The complex {[HLPdCl]Cl × H2O}2 (2Pd) has a square‐planar coordination around the Pd ion. It forms discrete dimers by intermolecular hydrogen bonding involving the protonated ligand HL. The coordination around the Zn2+ ion in {[(H2O)LZn]CF3SO3 × 2 H2O}∞ (3Zn) is best described as distorted trigonal‐bipyramidal. The N3O2 ligand sphere is composed of three nitrogen atoms from the bpa ligand, one water molecule, and a carboxylate oxygen atom from a neighbouring molecule, thus forming infinite chains along the crystallographic a axis. Further intermolecular interactions are based on the same (H2O)2(anion)2 motif as for 2Pd, but whereas the former forms discrete dimers, 3Zn forms a more complicated two‐dimensional coordination polymer with additional intermolecular hydrogen bonds.