bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mode locked and distributed feedback silicon evanescent lasers
Authors: Koch B.R. , Fang A.W. , Lively E. , Jones R. , Cohen O. , Blumenthal D.J. , Bowers J.E. 
Published: November 2008

AbstractElectrically pumped lasers that can be made on silicon and integrated with other components are important in order to take full advantage of the capabilities of silicon photonics. In this paper we review two specific types of hybrid silicon evanescent lasers that can fulfill these requirements. We discuss recent results of distributed feedback (DFB) lasers and mode locked lasers made on silicon using evanescent coupling to thin films of III‐V material. Device designs and test results are discussed in detail.
ZnCdO/ZnO – a new heterosystem for green‐wavelength semiconductor lasing
Authors: Kalusniak S. , Sadofev S. , Puls J. , Henneberger F. 
Published: November 2008

AbstractWe report on our efforts to cultivate the ternary compound ZnCdO as a semiconductor laser material. Molecular beam epitaxy far from thermal equilibrium allows us to overcome the standard solubility limit and to fabricate alloys with band gaps ranging from 3.4 down to 2.1 eV. Optimized structures containing well‐defined quantum wells as active zones are capable of low‐threshold lasing under optical pumping up to room temperature. The longest lasing wavelength achieved so far is 510 nm.
Advances in analysis of microbial metabolic fluxes via 13C isotopic labeling
Authors: Tang Yinjie J. , Martin Hector Garcia , Myers Samuel , Rodriguez Sarah , Baidoo Edward E.K. , Keasling Jay D. 
Published: November 2008

AbstractMetabolic flux analysis via 13C labeling (13C MFA) quantitatively tracks metabolic pathway activity and determines overall enzymatic function in cells. Three core techniques are necessary for 13C MFA: (1) a steady state cell culture in a defined medium with labeled‐carbon substrates; (2) precise measurements of the labeling pattern of targeted metabolites; and (3) evaluation of the data sets obtained from mass spectrometry measurements with a computer model to calculate the metabolic fluxes. In this review, we summarize recent advances in the 13C‐flux analysis technologies, including mini‐bioreactor usage for tracer experiments, isotopomer analysis of metabolites via high resolution mass spectrometry (such as GC‐MS, LC‐MS, or FT‐ICR), high performance and large‐scale isotopomer modeling programs for flux analysis, and the integration of fluxomics with other functional genomics studies. It will be shown that there is a significant value for 13C‐based metabolic flux analysis in many biological research fields. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 28:362–375, 2009
Improving performance through vertical disintegration: evidence from UK manufacturing firms
Authors: Desyllas Panos 
Published: November 2008

AbstractUnlike previous work on the vertical integration–performance relationship, we investigate the performance consequences of vertical disintegration. We offer a theoretical justification for the disintegration decision and we condition the disintegration effect on performance on the initial degree of firm integration, the timing and the direction of disintegration. Using a sample of UK manufacturing firms and controlling for disintegration endogeneity, we find that disintegration eventually results in improved operating performance, particularly when disintegration occurs as a reaction to poor performance and in cases of forward between‐sector disintegration. However, being highly integrated does not guarantee gains from disintegration. The implications of these findings are discussed. Copyright © 2008 John Wiley & Sons, Ltd.
Movement Disorder Society‐sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS‐UPDRS): Scale presentation and clinimetric testing results
Authors: Goetz Christopher G. , Tilley Barbara C. , Shaftman Stephanie R. , Stebbins Glenn T. , Fahn Stanley , Martinez‐Martin Pablo , Poewe Werner , Sampaio Cristina , Stern Matthew B. , Dodel Richard , Dubois Bruno , Holloway Robert , Jankovic Joseph , Kulisevsky Jaime , Lang Anthony E. , Lees Andrew , Leurgans Sue , LeWitt Peter A. , Nyenhuis David , Olanow C. Warren , Rascol Olivier , Schrag Anette , Teresi Jeanne A. , van Hilten Jacobus J. , LaPelle Nancy 
Published: November 2008

AbstractWe present a clinimetric assessment of the Movement Disorder Society (MDS)‐sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS‐UPDRS). The MDS‐UDPRS Task Force revised and expanded the UPDRS using recommendations from a published critique. The MDS‐UPDRS has four parts, namely, I: Non‐motor Experiences of Daily Living; II: Motor Experiences of Daily Living; III: Motor Examination; IV: Motor Complications. Twenty questions are completed by the patient/caregiver. Item‐specific instructions and an appendix of complementary additional scales are provided. Movement disorder specialists and study coordinators administered the UPDRS (55 items) and MDS‐UPDRS (65 items) to 877 English speaking (78% non‐Latino Caucasian) patients with Parkinson's disease from 39 sites. We compared the two scales using correlative techniques and factor analysis. The MDS‐UPDRS showed high internal consistency (Cronbach's alpha = 0.79–0.93 across parts) and correlated with the original UPDRS (ρ = 0.96). MDS‐UPDRS across‐part correlations ranged from 0.22 to 0.66. Reliable factor structures for each part were obtained (comparative fit index > 0.90 for each part), which support the use of sum scores for each part in preference to a total score of all parts. The combined clinimetric results of this study support the validity of the MDS‐UPDRS for rating PD. © 2008 Movement Disorder Society
Repairs of complex groin wounds with contralateral rectus abdominis myocutaneous flaps
Authors: Qi Fazhi , Zhang Yong , Gu Jianying 
Published: November 2008

AbstractManagement of complex groin wounds posterior to complications of vascular prosthetic surgery, malignant tumor excision, and irradiation therapy for recurrent cancers continued to pose a difficult task in reconstructive surgery. Pedicled and microsurgical myocutaneous flaps are valuable tools for wound repairs, but applications of these flaps are limited when the healthy vascular vessels are not available around the wound. In this report, we present our experience on the use of the contralateral rectus abdominis myocutaneous flaps for the coverage of the groin complex wounds in 13 patients. All the flaps were completely survived and the wounds healed uneventfully. The results suggest that the contralateral myocutaneous flap can be used for the repair of the groin wound with presence of significant comorbidities in the area, in which the ipsilateral local flaps and microsurgical flaps are not available. © 2008 Wiley‐Liss, Inc. Microsurgery, 2009.
On the global existence and small dispersion limit for a class of complex Ginzburg–Landau equations
Authors: Gao Hongjun , Wang Xueqin 
Published: November 2008

AbstractIn this paper we consider a class of complex Ginzburg–Landau equations. We obtain sufficient conditions for the existence and uniqueness of global solutions for the initial‐value problem in d‐dimensional torus 𝕋d, and that solutions are initially approximated by solutions of the corresponding small dispersion limit equation for a period of time that goes to infinity as dispersive coefficient goes to zero. Copyright © 2008 John Wiley & Sons, Ltd.
Complete assignment of 1H and 13C NMR data of pravastatin derivatives
Authors: Bacher Markus , Baumann Karl , Knapp Hermann , Steck Andrea , Teibl Sigrid 
Published: November 2008

AbstractThe complete 1H and 13C NMR data of 27 pravastatin derivatives are presented. Assignment was achieved by use of 1D and 2D NMR experiments (selective 1D NOE, COSY, NOESY, HSQC, HMBC). Copyright © 2008 John Wiley & Sons, Ltd.
Gleaning multicomponent T1 and T2 information from steady‐state imaging data
Authors: Deoni Sean C.L. , Rutt Brian K. , Arun Tarunya , Pierpaoli Carlo , Jones Derek K. 
Published: November 2008

AbstractThe driven‐equilibrium single‐pulse observation of T1 (DESPOT1) and T2 (DESPOT2) are rapid, accurate, and precise methods for voxelwise determination of the longitudinal and transverse relaxation times. A limitation of the methods, however, is the inherent assumption of single‐component relaxation. In a variety of biological tissues, in particular human white matter (WM) and gray matter (GM), the relaxation has been shown to be more completely characterized by a summation of two or more relaxation components, or species, each believed to be associated with unique microanatomical domains or water pools. Unfortunately, characterization of these components on a voxelwise, whole‐brain basis has traditionally been hindered by impractical acquisition times. In this work we extend the conventional DESPOT1 and DESPOT2 approaches to include multicomponent relaxation analysis. Following numerical analysis of the new technique, renamed multicomponent driven equilibrium single pulse observation of T1/T2 (mcDESPOT), whole‐brain multicomponent T1 and T2 quantification is demonstrated in vivo with clinically realistic times of between 16 and 30 min. Results obtained from four healthy individuals and two primary progressive multiple sclerosis (MS) patients demonstrate the future potential of the approach for identifying and assessing tissue changes associated with several neurodegenerative conditions, in particular those associated with WM. Magn Reson Med 60:1372–1387, 2008. © 2008 Wiley‐Liss, Inc.
A single‐scan T mapping method based on two gradient‐echo images with compensation for macroscopic field inhomogeneity
Authors: Meng Yuguang , Lei Hao 
Published: November 2008

AbstractT‐weighted imaging (TWI) and quantitative T mapping with conventional gradient‐echo acquisition are often hindered by severe signal loss induced by macroscopic field inhomogeneity. Various z‐shimming approaches have been developed for TWI/T mapping in which the effects of macroscopic field inhomogeneity are suppressed while the sensitivity of T‐related signal intensity to alterations in the microscopic susceptibility is maintained. However, this is often done at the cost of significantly increased imaging time. In this work, a fast T mapping method with compensation for macroscopic field inhomogeneity was developed. A proton density‐weighted image and a composite T‐weighted image, both of which were essentially free from macroscopic field inhomogeneity‐induced signal loss, were used for the T calculation. The composite T‐weighted image was reconstructed from a number of gradient‐echo images acquired with successively incremented z‐shimming compensation. Because acquisition of the two images and z‐shimming compensation were realized in a single scan, the total acquisition time for obtaining a T map with the proposed method is the same as the time taken for a conventional multiecho gradient‐echo imaging sequence without compensation. The performance and efficiency of the proposed method were demonstrated and evaluated at 4.7 T. Magn Reson Med 60:1388–1395, 2008. © 2008 Wiley‐Liss, Inc.
High‐resolution maps of magnetization transfer with inherent correction for RF inhomogeneity and T1 relaxation obtained from 3D FLASH MRI
Authors: Helms Gunther , Dathe Henning , Kallenberg Kai , Dechent Peter 
Published: November 2008

AbstractAn empirical equation for the magnetization transfer (MT) FLASH signal is derived by analogy to dual‐excitation FLASH, introducing a novel semiquantitative parameter for MT, the percentage saturation imposed by one MT pulse during TR. This parameter is obtained by a linear transformation of the inverse signal, using two reference experiments of proton density and T1 weighting. The influence of sequence parameters on the MT saturation was studied. An 8.5‐min protocol for brain imaging at 3 T was based on nonselective sagittal 3D‐FLASH at 1.25 mm isotropic resolution using partial acquisition techniques (TR/TE/α = 25ms/4.9ms/5° or 11ms/4.9ms/15° for the T1 reference). A 12.8 ms Gaussian MT pulse was applied 2.2 kHz off‐resonance with 540° flip angle. The MT saturation maps showed an excellent contrast in the brain due to clearly separated distributions for white and gray matter and cerebrospinal fluid. Within the limits of the approximation (excitation <15°, TR/T1 ≪ 1) the MT term depends mainly on TR, the energy and offset of the MT pulse, but hardly on excitation and T1 relaxation. It is inherently compensated for inhomogeneities of receive and transmit RF fields. The MT saturation appeared to be a sensitive parameter to depict MS lesions and alterations of normal‐appearing white matter. Magn Reson Med 60:1396–1407, 2008. © 2008 Wiley‐Liss, Inc.
Efficient 1H to 31P polarization transfer on a clinical 3T MR system
Authors: Klomp D.W.J. , Wijnen J.P. , Scheenen T.W.J. , Heerschap A. 
Published: November 2008

Abstract31P MR spectroscopy (MRS) in the detection of phosphocholine (PC), glycerolphosphocholine (GPC), phosphorylelthanolamine (PE), and glycerolphosphoethanolamine (GPE) compounds has shown clinical potential at 1.5T for several human diseases. The use of 1H to 31P polarization transfer can improve the sensitivity using a refocused INEPT method with a potential enhancement of 2.4 (γ1H/γ31P). However, in this method the 31P signals of PE, PC, GPE, and GPC are strongly attenuated (50% or more) due to J‐coupling between 31P and 1H that have similar magnitudes for homonuclear J‐coupling constants in those metabolites. A method to cancel the homonuclear J‐coupling effects in polarization transfer experiments is to apply frequency‐selective refocusing pulses, which becomes feasible at 3T due to the increased chemical shift dispersion as compared to 1.5T. In this study, full 1H to 31P polarization transfer was realized using chemical shift selective refocusing pulses at 3T. T1 and T2 values for 1H and 31P spins of PE, PC, GPE, and GPC were measured in the human brain. A more than 2‐fold signal‐to‐noise ratio (SNR) improvement was obtained compared to an optimized direct 31P MRS method. As shifted RF pulses were used, this method can be applied on a broadband clinical MR system with a single RF system. Magn Reson Med 60:1298–1305, 2008. © 2008 Wiley‐Liss, Inc.
Characterizing fiber directional uncertainty in diffusion tensor MRI
Authors: Jeong Ha‐Kyu , Anderson Adam W. 
Published: November 2008

AbstractImage noise in diffusion tensor MRI (DT‐MRI) causes errors in the measured tensor and hence variance in the estimated fiber orientation. Uncertainty in fiber orientation has been described using a circular “cone of uncertainty” (CU) around the principal eigenvector of the DT. The CU has proved to be a useful construct for quantifying and visualizing the variability of DT‐MRI parameters and fiber tractography. The assumption of circularity of the CU has not been tested directly, however. In this work, bootstrap analysis and simple theoretical arguments were used to show that the CU is elliptical and multivariate normal in the vast majority of white matter (WM) voxels for typical measurement conditions. The dependence of the cone angle on the signal‐to‐noise ratio (SNR) and eigenvalue contrast was established. The major and minor cone axes are shown to be coincident with the second and third eigenvectors of the tensor, respectively, in the limit of many uniformly spaced diffusion‐encoding directions. The deviation between the major cone axis and the second eigenvector was quantified for typical sets of diffusion‐weighting (DW) directions. The elliptical CU provides more realistic error information for fiber‐tracking algorithms and a quantitative basis for selecting DT imaging acquisition protocols. Magn Reson Med 60:1408–1421, 2008. © 2008 Wiley‐Liss, Inc.
Slice‐selective RF pulses for in vivo B inhomogeneity mitigation at 7 tesla using parallel RF excitation with a 16‐element coil
Authors: Setsompop Kawin , Alagappan Vijayanand , Gagoski Borjan , Witzel Thomas , Polimeni Jonathan , Potthast Andreas , Hebrank Franz , Fontius Ulrich , Schmitt Franz , Wald Lawrence L. , Adalsteinsson Elfar 
Published: November 2008

AbstractSlice‐selective RF waveforms that mitigate severe B inhomogeneity at 7 Tesla using parallel excitation were designed and validated in a water phantom and human studies on six subjects using a 16‐element degenerate stripline array coil driven with a butler matrix to utilize the eight most favorable birdcage modes. The parallel RF waveform design applied magnitude least‐squares (MLS) criteria with an optimized k‐space excitation trajectory to significantly improve profile uniformity compared to conventional least‐squares (LS) designs. Parallel excitation RF pulses designed to excite a uniform in‐plane flip angle (FA) with slice selection in the z‐direction were demonstrated and compared with conventional sinc‐pulse excitation and RF shimming. In all cases, the parallel RF excitation significantly mitigated the effects of inhomogeneous B on the excitation FA. The optimized parallel RF pulses for human B mitigation were only 67% longer than a conventional sinc‐based excitation, but significantly outperformed RF shimming. For example the standard deviations (SDs) of the in‐plane FA (averaged over six human studies) were 16.7% for conventional sinc excitation, 13.3% for RF shimming, and 7.6% for parallel excitation. This work demonstrates that excitations with parallel RF systems can provide slice selection with spatially uniform FAs at high field strengths with only a small pulse‐duration penalty. Magn Reson Med 60:1422–1432, 2008. © 2008 Wiley‐Liss, Inc.
Functional MRI with magnetization transfer effects: Determination of BOLD and arterial blood volume changes
Authors: Kim Tae , Hendrich Kristy , Kim Seong‐Gi 
Published: November 2008

AbstractThe primarily intravascular magnetization transfer (MT)‐independent changes in functional MRI (fMRI) can be separated from MT‐dependent changes. This intravascular component is dominated by an arterial blood volume change (ΔCBVa) term whenever venous contributions are minimized. Stimulation‐induced ΔCBVa can therefore be measured by a fit of signal changes to MT ratio. MT‐varied fMRI data were acquired in 13 isoflurane‐anesthetized rats during forepaw stimulation at 9.4T to simultaneously measure blood‐oxygenation‐level–dependent (BOLD) and ΔCBVa response in somatosensory cortical regions. Transverse relaxation rate change (ΔR2) without MT was –0.43 ± 0.15 s−1, and MT ratio decreased during stimulation. ΔCBVa was 0.46 ± 0.15 ml/100 g, which agrees with our previously‐presented MT‐varied arterial‐spin‐labeled data (0.42 ± 0.18 ml/100 g) in the same animals and also correlates with ΔR2 without MT. Simulations show that ΔCBVa quantification errors due to potential venous contributions are small for our conditions. Magn Reson Med 60:1518–1523, 2008. © 2008 Wiley‐Liss, Inc.
Pharmacokinetic modeling of delayed gadolinium enhancement in the myocardium
Authors: Knowles Benjamin R. , Batchelor Philip G. , Parish Victoria , Ginks Matthew , Plein Sven , Razavi Reza , Schaeffter Tobias 
Published: November 2008

AbstractDelayed contrast‐enhanced magnetic resonance imaging (DCE‐MRI) provides prognostic information by delineating regions of myocardial scar. The mechanism of this delayed enhancement in myocardial infarctions (MIs) is hypothesized to result from altered kinetics and changes in the volumes of distribution in the myocardium. Pharmacokinetic models with two and three compartments were fitted to the concentration‐time curves of dynamic contrast‐enhanced MRI data obtained from five patients with known MI. Furthermore, the parameter stability was investigated in simulations for the two different models. The transfer constants and volumes of distribution showed a good correlation with imaging findings on early and delayed contrast‐enhanced MRI. The two compartment model showed higher parameter stability. The three compartment model allows a more in‐depth quantification of myocardial scarring. These models have the potential to improve the diagnosis of myocardial pathologies involving scar, with differing kinetics and volumes of distribution such as infarction or cardiomyopathy. Magn Reson Med 60:1524–1530, 2008. © 2008 Wiley‐Liss, Inc.
Hypercapnia‐induced effects on image contrast based on intermolecular double‐quantum coherences
Authors: Schäfer Andreas , Zysset Stefan , Heinke Wolfgang , Möller Harald E. 
Published: November 2008

AbstractIntermolecular double‐quantum coherences (iDQCs) are well known to be sensitive to magnetic‐field perturbations inside tissues. However, the exact relation between iDQC contrast in magnetic resonance imaging (MRI) and the underlying physiology is less well understood. To investigate parameters that influence iDQC signal changes observed during neuronal activation, carbogen‐inhalation experiments were performed to produce a pure hemodynamic response without affecting oxidative metabolism. Eight human volunteers were studied at 2.9 T using gradient‐recalled echo (GRE) and spin‐echo (SE) variants of a single‐shot sequence selecting iDQCs. Results were compared with conventional recordings of the blood oxygen level‐dependent (BOLD) effect. Maps of voxels responding to the carbogen challenge showed similar distributions for iDQC and conventional MRI after adjustment for different sensitivities. Strong diffusion weighting of iDQC sequences and transverse relaxation effects suggested quantitative suppression of intravascular signal contributions. A particular susceptibility to local gradients during the evolution period (in which iDQCs evolve at twice the Larmor frequency) plus a strong relaxation weighting during the detection period due to the use of a long echo time (for refocusing of the dipolar signal) produced iDQC signal changes up to 21.7% ± 2.5%. These results agreed quantitatively with computations based on the balloon model of BOLD‐weighted MRI without requiring further assumptions. Magn Reson Med 60:1306–1312, 2008. © 2008 Wiley‐Liss, Inc.
Single‐shot multiecho parallel echo‐planar imaging (EPI) for diffusion tensor imaging (DTI) with improved signal‐to‐noise ratio (SNR) and reduced distortion
Authors: Nana Roger , Zhao Tiejun , Hu Xiaoping 
Published: November 2008

AbstractIn this work, a multiecho parallel echo‐planar imaging (EPI) acquisition strategy is introduced as a way to improve the acquisition efficiency in parallel diffusion tensor imaging (DTI). With the use of an appropriate echo combination strategy, the sequence can provide signal‐to‐noise ratio (SNR) enhancement while maintaining the advantages of parallel EPI. Simulations and in vivo experiments demonstrate that a weighted summation of multiecho images provides a significant gain in SNR over the first echo image. It is experimentally demonstrated that this SNR gain can be utilized to reduce the number of measurements often required to ensure adequate SNR for accurate DTI measures. Furthermore, the multiple echoes can be used to derive a T2 map, providing additional information that might be useful in some applications. Magn Reson Med 60:1512–1517, 2008. © 2008 Wiley‐Liss, Inc.