bluuebunny/crossref_metadata_2025_split huggingface dataset:
MRI of bone tumors: Fast STIR imaging as a substitute for T1‐weighted contrast‐enhanced fat‐suppressed spin‐echo imaging
Authors: Tokuda Osamu , Hayashi Noriko , Matsunaga Naofumi 
Published: March 2004

AbstractPurposeTo compare the usefulness of short inversion recovery (STIR) and T1‐weighted, contrast‐enhanced, fat‐suppressed (T1W‐CEFS) sequences for the evaluation of bone tumors.Materials and MethodsEighteen patients with 19 bone tumors who underwent both STIR and T1W‐CEFS imaging were evaluated. The tumors were categorized in pairs as follows: bone marrow and soft‐tissue components, benign and malignant tumors, and tumors with and without mineralization. The signal difference‐to‐noise ratio (SDNR), signal‐to‐noise ratio (SNR), and tumor volume were calculated in each group. An additional qualitative analysis was performed by means of the ratings of imaging contrast.ResultsThe mean SDNRs of all bone marrow components and bone marrow components without mineralization were significantly higher on fast STIR images than on T1W‐CEFS images (P < 0.05). There was no significant difference in the mean SDNR and SNR of the other group (surrounding soft tissue components, bone marrow components with mineralization, benign and malignant lesions) between fast STIR images and T1W‐CEFS images. The mean volume of the tumors was significantly higher with STIR than with the T1W‐CEFS sequence (P < 0.05).ConclusionThe STIR sequence should be used instead of T1W‐CEFS imaging for the evaluation of bone tumors. J. Magn. Reson. Imaging 2004;19:475–481. © 2004 Wiley‐Liss, Inc.
Correction of spatial distortion in EPI due to inhomogeneous static magnetic fields using the reversed gradient method
Authors: Morgan Paul S. , Bowtell Richard W. , McIntyre Dominick J.O. , Worthington Brian S. 
Published: March 2004

AbstractPurposeTo derive and implement a method for correcting spatial distortion caused by in vivo inhomogeneous static magnetic fields in echo‐planar imaging (EPI).Materials and MethodsThe reversed gradient method, which was initially devised to correct distortion in images generated by spin‐warp MRI, was adapted to correct distortion in EP images. This method provides point‐by‐point correction of distortion throughout the image. EP images, acquired with a 3 T MRI system, of a phantom and a volunteer's head were used to test the correction method.ResultsGood correction was observed in all cases. Spatial distortion in the uncorrected images ranged up to 4 pixels (12 mm) and was corrected successfully.ConclusionThe correction was improved by the application of a nonlinear interpolation scheme. The correction requires that two EP images be acquired at each slice position. This increases the acquisition time, but an improved signal‐to‐noise ratio (SNR) is seen in the corrected image. The local SNR gain decreases with increasing distortion. In many EPI acquisition schemes, multiple images are averaged at each slice position to increase the SNR; in such cases the reversed gradient correction method can be applied with no increase in acquisition duration. J. Magn. Reson. Imaging 2004;19:499–507. © 2004 Wiley‐Liss, Inc.
Metabolites of an orally active antimicrobial prodrug, 2,5‐bis(4‐amidinophenyl)furan‐bis‐O‐methylamidoxime, identified by liquid chromatography/tandem mass spectrometry
Authors: Zhou Lian , Thakker Dhiren R. , Voyksner Robert D. , Anbazhagan Mariappan , Boykin David W. , Hall James E. , Tidwell Richard R. 
Published: March 2004

AbstractDB75 (2,5‐bis(4‐amidinophenyl)furan) is a promising antimicrobial agent against African trypanosomiasis and Pneumocystis carinii pneumonia. However, it suffers from poor oral activity in rodent models for both infections. In contrast, a novel prodrug of DB75, 2,5‐bis(4‐amidinophenyl)furan‐bis‐O‐methylamidoxime (DB289), has excellent oral activity. DB289 is currently undergoing clinical investigation as a candidate drug to treat primary stage African trypanosomiasis and Pneumocystis carinii pneumonia. In this study, metabolites of DB289 formed after incubation with freshly isolated rat hepatocytes were characterized using liquid chromatography/ion trap mass spectrometry. Administration of DB289 and octadeuterated DB289 in a 1 : 1 mixture greatly facilitated metabolite identification by providing isotope patterns with twin ions separated by 8 m/z units in the ratio 1 : 1, in the extracted ion chromatograms of molecular ions and in the product ion mass spectra of metabolites. Ten metabolites were identified. Series of O‐demethylations and N‐dehydroxylations led to the metabolic activation of DB289 to DB75 with the production of four intermediate phase I metabolites. Phase II glucuronidation and sulfation led to the formation of four glucuronide and one sulfate metabolites. Copyright © 2004 John Wiley & Sons, Ltd.
Peak capacity of ion mobility mass spectrometry: the utility of varying drift gas polarizability for the separation of tryptic peptides
Authors: Ruotolo Brandon T. , McLean John A. , Gillig Kent J. , Russell David H. 
Published: March 2004

AbstractIon mobility mass spectrometry (IM‐MS) peptide mass mapping experiments were performed using a variety of drift gases (He, N2, Ar and CH4). The drift gases studied cover a range of polarizabilities ((0.2–2.6) × 10−24 cm3) and the peak capacities obtained for tryptic peptides in each gas are compared. Although the different gases exhibit similar peak capacities (5430 (Ar) to 7580 (N2)) in some cases separation selectivity presumably based on peptide conformers (or conformer populations), is observed. For example the drift time profiles observed for some tryptic peptide ions from aldolase (rabbit muscle) show a dependence on drift gas. The transmission of high‐mass ions (m/z > 2000) is also influenced by increased scattering cross‐section of the more massive drift gases. Consequently the practical peak capacity for IM‐MS separation cannot be assumed to be solely a function of resolution and the ability of a gas to distribute signals in two‐dimensional space; rather, peak capacity estimates must account for the transmission losses experienced for peptide ions as the drift gas mass increases. Copyright © 2004 John Wiley & Sons, Ltd.
Mass spectrometry of 1,3‐ and 1,5‐dicaffeoylquinic acids
Authors: Schram Karl , Miketova Petra , Slanina Jiri , Humpa Otakar , Taborska Eva 
Published: March 2004

AbstractSamples of 1,3‐ (1) and 1,5‐dicaffeoylquinic acid (2) and their hexaacetate derivatives were examined using positive and negative electrospray ionization mass spectrometry and tandem mass spectrometry. Differences in the various spectra allow the discrimination of each of the isomers. Specific losses in the spectra of 2 also permit the identification of the site of substitution of one of the caffeic acid moieties as being at the 5‐position. The spectra of 3,5‐ (3) and 4,5‐dicaffeoylquinic (4) acids and their hexaacetate derivatives were compared with those of 1 and 2 and their derivatives, and differences in ion abundances or the presence/absence of specific ions can be used to identify uniquely each of the compounds. Copyright © 2004 John Wiley & Sons, Ltd.
Observation of self‐ion–molecule reactions during collisionally activated dissociation in an ion‐trap mass spectrometer
Authors: Wu Hui‐Fen , Chen Chien‐Hung , Wu Meng‐Ting 
Published: March 2004

AbstractThis paper describes the formation of protonated molecules ([M + H]+) and adduct ions by self‐ion–molecule reactions (SIMR) during collisionally activated decomposition (CAD) of methyne addition ions ([M + CH]+) produced from chemical ionization (CI) or SIMR in both an external and internal source ion‐trap mass spectrometer (ITMS). The CAD results for the methyne addition ions of dopamine produced from both SIMR and dimethyl ether CI undertaken in the external and internal source ITMS were compared in order to prove the occurrence of SIMR during CAD processes. Compared with the external source ITMS, the internal source ITMS is much more easily applicable to this type of reaction owing to the large population of neutral analytes present in the trap. Copyright © 2004 John Wiley & Sons, Ltd.
Alternative approaches for the detection of various phospholipid classes by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Authors: Estrada Rosendo , Yappert M. Cecilia 
Published: March 2004

AbstractThe detection of phospholipids (PLs) by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry was demonstrated nearly a decade ago. However, its use as a conventional tool for PL analysis has been hindered by ambiguities in peak assignments caused by spectral overlaps and difficulties in the detection of some PL classes when analytes with positively charged head groups, such as sphingomyelins (SMs) and phosphatidylcholines (PCs) are present. In this work, either a strong cation‐exchange resin or CsCl crystals were added directly to the PL samples to reduce spectral complexity and enhance sensitivity. The quantitative exchange resulted in virtually only protonated or Cs+ adducts. To alleviate difficulties in the detection and identification of PL classes with ionization efficiencies lower than those of SMs and PCs, improvements in the sensitivity of negative‐ion mass spectra were sought. For this purpose, several neutral and basic matrices were tried. Among them, p‐nitroaniline (PNA) proved to be an advantageous alternative to the use of 2,5‐dihydroxybenzoic acid (DHB), the most commonly used matrix in PL analysis. Because of its lower acidity, PNA increased the relative amount of deprotonated species and improved the sensitivity of negative‐ion mass spectra. It was possible to confirm peak assignments for PL classes that normally give weak signals when DHB is used. Noteworthy is the detection (in both positive and negative modes) and conclusive identification of species in natural mixtures of phosphatidylethanolamines (PEs) and PE plasmalogens (PEps). PNA allowed the identification of PEs and PEps even in mixtures containing SMs and PCs. Although some cations related to PCs and PEs overlapped in positive‐ion spectra, these interferences were eliminated in the negative mode as only the deprotonated forms of PEs and PEps were detectable and those of SMs and PCs were absent owing to their neutrality. Copyright © 2004 John Wiley & Sons, Ltd.
Simple and sensitive liquid chromatographic quantitative analysis of the novel marine anticancer drug Yondelis™ (ET‐743, trabectedin) in human plasma using column switching and tandem mass spectrometric detection
Authors: Stokvis E. , Rosing H. , López‐Lázaro L. , Beijnen J. H. 
Published: March 2004

AbstractThe development of a simple and sensitive assay for the quantitative analysis of the marine anticancer agent Yondelis (ET‐743, trabectedin) in human plasma using liquid chromatography (LC) with column switching and tandem mass spectrometric (MS/MS) detection is described. After protein precipitation with methanol, diluted extracts were injected on to a small LC column (10 × 3.0 mm i.d.) for on‐line concentration and further clean‐up of the sample. Next, the analyte and deuterated internal standard were back‐flushed on to an analytical column for separation and subsequent detection in an API 2000 triple‐quadrupole mass spectrometer. The lower limit of quantitation was 0.05 ng mL−1 using 100 µl of plasma with a linear dynamic range up to 2.5 ng ml−1. Validation of the method was performed according to the most recent FDA guidelines for bioanalytical method validation. The time needed for off‐line sample preparation has been reduced 10‐fold compared with an existing LC/MS/MS method for ET‐743 in human plasma, employing a labor‐intensive solid‐phase extraction procedure for sample pretreatment. The proposed column switching method was successfully applied in phase II clinical trials with Yondelis and pharmacokinetic monitoring. Copyright © 2004 John Wiley & Sons, Ltd.
Application of liquid chromatography‐ion trap mass spectrometry to the characterization of the 16‐membered ring macrolide josamycin propionate
Authors: Govaerts Cindy , Chepkwony Hezekiah Kibet , Van Schepdael Ann , Adams Erwin , Roets Eugène , Hoogmartens Jos 
Published: March 2004

AbstractCoupled liquid chromatography and ion trap mass spectrometry (LC/MS) was used for the characterization of the semi‐synthetic 16‐membered ring macrolide josamycin propionate. On‐line identification of impurities in this antibiotic complex was performed with an ion trap mass spectrometer without recourse to time‐consuming isolation and purification procedures. Ion trap mass spectrometry is ideally suited to identification of impurities because it provides MSn capability, enabling multiple stages of mass spectrometry to obtain the maximum amount of structural information for a given molecule. The ion trap was used with an electrospray ionization source operated in the positive ion mode or with an atmospheric pressure chemical ionization source operated in the negative ion mode. The identity of the unknown compounds was deduced using the MS/MS and MSn collision‐induced dissociation spectra of reference substances or structural analogs as interpretative templates, combined with knowledge about the nature of functional group fragmentation behavior. Given the importance attached to the identification of impurities of unknown identity in pharmaceutical substances, this study is useful for companies producing josamycin propionate. The knowledge of the fragmentation behavior is also of importance in further research on other 16‐membered macrolides. Copyright © 2004 John Wiley & Sons, Ltd.
Modelling PBG devices to DWDM filters design
Authors: Giorgio Agostino , Pasqua Decio , Gina Perri Anna 
Published: March 2004

AbstractThe fibre optic transmission systems require a bandwidth of about 25 THz in telecommunications networks, for which it is necessary to resort to dense wavelength division multiplexing (DWDM) systems. These systems need optical filters to broadcast selectively or not in a given wavelength band.A new very promising technology for these applications is the photonic crystals with forbidden bandgap (photonic bandgap (PBG)).In this paper, we propose a model of PBG devices to design DWDM filters on PBG materials. Copyright © 2004 John Wiley & Sons, Ltd.
SSOR preconditioned GMRES for the FEM analysis of waveguide discontinuities with anisotropic dielectric
Authors: Chen R. S. , Ping X. W. , Wang D. X. , K. N. Yung Edward 
Published: March 2004

AbstractThe anisotropic media and active properties of the perfectly matched layer (PML) absorbers significantly deteriorate the finite element method (FEM) system condition and as a result, convergence of the iterative solver is substantially slowed down. To address this issue, the symmetric successive over‐relaxation (SSOR) preconditioning scheme is applied to the generalized minimal residual (GMRES) for solving a large sparse and non‐symmetric system of linear equations resulting from the analysis of ferrite waveguide device by use of edge‐based FEM. Consequently, this preconditioned GMRES (PGMRES) approach can reach convergence ten times faster than GMRES for the typical structures. Copyright © 2004 John Wiley & Sons, Ltd.
The crosstalk characteristics of different PCB layouts with multiconductor transmission line
Authors: Ding C. H. , Wu S. D. , Chou J. H. 
Published: March 2004

AbstractA simple method of moment numerical scheme is adopted to study the crosstalk characteristics of printed circuit board. Both strip lines and microstrips PCB configurations are investigated. The results indicate that with the ground plane closer to the signal line, the crosstalk voltages can be reduced. Furthermore, the non‐synchronization due to difference in mode velocities can also be reduced. Copyright © 2004 John Wiley & Sons, Ltd.
Numerical approach to field fluctuations and spectral lineshape in InGaAsP laser diodes
Authors: Ahmed Moustafa 
Published: March 2004

AbstractThis paper reports on a numerical approach to model the field fluctuations, spectral lineshape and linewidth in semiconductor lasers. The approach is based on numerical solution of the laser rate equations augmented by Langevin noise sources that account for fluctuations in the lasing field. The paper newly examines contributions of intensity and frequency noises to the spectral characteristics of the lineshape and its linewidth over a wide range of injection current. The model is applied to InGaAsP lasers emitting in a wavelength of 1.5 μm as the most representative light sources in optical communication systems. Accuracy of approximated models of calculating linewidth from low‐frequency components of the frequency noise is checked. Effect of non‐linear gain suppression on the lineshape is also explored. The spectral lineshape promotes and the linewidth decreases as the laser is injected far from the near‐threshold region. The lineshape changes mainly with changes in the frequency noise spectrum while the linewidth is sensitive to variation in the low‐frequency levels of both intensity and frequency noises. Copyright © 2004 John Wiley & Sons, Ltd.
Time‐domain simulation of power transients in Raman fibre amplifiers
Authors: Karásek M. , Kaňka J. , Honzátko P. , Peterka P. 
Published: March 2004

AbstractWe study power transients in Raman fibre amplifiers (RFA). Transients are defined as the output signal power response to abrupt change in the number of signal channels at the input to the RFA (channel addition/removal). The simulations are based on application of a large signal numerical model which incorporates time variation effects, downstream propagation of multiple signals, upstream propagation of pump and both downstream and upstream propagation of amplified spontaneous emission (ASE). System of coupled non‐linear differential equations describing the propagation of the signal, pump and ASE waves along the RFA and their evolution in time represents a two‐boundary value problem. Due to the backward propagating ASE and counter‐directional pumping, an iterative forward and backward solution of propagation equations must be used in order to achieve a steady‐state distribution of signals, pumps, and ASE powers along the RFA. We have used either the fourth‐order Runge–Kutta routine, or an alternative average power analysis (APA) approach to obtain the steady‐state optical power distribution along the fibre. Direct integration is used to obtain time evolution of optical powers as a response to channel addition/removal. Stability of the numerical solution depends on the relation of discretization steps in space and time. Gain locking of the RFA via electronic feedforward pump control derived from a monitoring channel output power has been introduced in the model to study the possibility of suppressing the surviving channel power fluctuations. Copyright © 2004 John Wiley & Sons, Ltd.
Inhibition of patulin production by Penicillium expansum cultured with neem (Azadirachta indica) leaf extracts
Authors: Aparecida Galerani Mossini Simone , De Oliveira Kesia Pires , Kemmelmeier Carlos 
Published: April 2004

AbstractAqueous extract of the leaves of neem [Azadirachta indica A. Juss (Meliaceae)] was tested in vitro for antifungal activity against Penicillium expansum. Patulin production was inhibited during cultivation, when concentrations higher than 50 mg/ml of neem leaf extract was added to the culture medium. Analyses of mycotoxin production were performed by TLCAbbreviations used: TLC, Thin layer chromatography; HPLC, High‐performance liquid chromatography; UEM, Universidade Estadual de Maringá [State University of Maringá]; IAPAR, Instituto Agrônomico do Paraná [Agronomy Institute of Paraná].
and HPLC. Fungal growth and colony characteristics, in the presence of the extract, were investigated and compared with extract‐free cultures. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
In‐Situ Atomic Force Microscopy Observation of Enzymatic Degradation in Poly(hydroxyalkanoic acid) Thin Films: Normal and Constrained Conditions
Authors: Kikkawa Yoshihiro , Hirota Takuya , Numata Keiji , Tsuge Takeharu , Abe Hideki , Iwata Tadahisa , Doi Yoshiharu 
Published: March 2004

AbstractSummary: The enzymatic degradation of lamellar crystals in poly(hydroxyalkanoic acid) thin films has been visualized by using in‐situ dynamic force mode (tapping mode) atomic force microscopy (AFM) in buffer solution. It was found that poly(hydroxybutyric acid) (PHB) depolymerase from Ralstonia pickettii T1 degraded the thin surface layers formed at room temperature first, and that lamellar crystals formed at the crystallization temperature (110 °C) were eroded from the crystallographic a‐axis to show splintered morphologies at the tips of the crystals. In some cases, lamellar crystals were hydrolyzed from the crystallographic b‐axis, resulting in the formation of small crevices. These results suggest that disordered molecular chain‐packing regions exist in the crystal along the crystallographic a‐ and b‐axes, and that enzymatic degradation predominantly occurs from these defective regions. In addition, cantilever‐tip‐induced enzymatic degradation was carried out in the presence of PHB depolymerase. A concave area was artificially formed on the stacked lamellar crystals by the AFM tip. In‐situ AFM observation has revealed that enzymatic degradation proceeds along both the longitudinal and lateral directions of the lamellae. At the same time, the PHB depolymerase preferentially eroded the concave area along the crystallographic c‐axis. These results demonstrated that the PHB depolymerase predominantly degrades the less‐ordered molecular chain‐packing regions in the crystals.A series of AFM images of a poly{[(R)‐3‐hydroxybutyric acid]‐co‐[8‐mol%‐(R)‐3‐hydroxyhexanoic acid]} thin film during the cantilever‐tip‐induced enzymatic degradation process.imageA series of AFM images of a poly{[(R)‐3‐hydroxybutyric acid]‐co‐[8‐mol%‐(R)‐3‐hydroxyhexanoic acid]} thin film during the cantilever‐tip‐induced enzymatic degradation process.
Involvement of Hevea Latex Organelle Membrane Proteins in the Rubber Biosynthesis Activity and Regulatory Function
Authors: Wititsuwaannakul Dhirayos , Rattanapittayaporn Atiya , Koyama Tanetoshi , Wititsuwaannakul Rapepun 
Published: March 2004

AbstractSummary: Centrifugation of fresh Hevea rubber latex yields three distinct fractions. The sediment bottom fraction (BF) content of membrane‐bound organelles is ca. 20 vol.‐% of latex. Prolonged storage or delayed use of fresh latex will result in disintegration and loss of the bottom fraction. This is due to the osmotically sensitive BF rupture and its membrane debris being tightly bound to the top rubber particles (RP) phase. The BF membrane was found to be highly active for rubber biosynthesis (RB), in contrast to previous reports that describe RB only occurring on the RP surface. It was clearly shown that washed BF membrane (WBM) was much more active than fresh RP for RB activity. WBM was highly activated by SDS for RB in a biphasic manner, but SDS strongly inhibited the RP. Probably WBM micelle formation resulted in a highly increased active surface area for RB. C55‐PP (UPP) was a very active allylic for WBM in RB function, but inactive for RP. Serial acetone extraction of WBM proteins showed a distinct profile of the fractions with different RB activity. WBM isolated proteins suspended in 2% sodium dodecyl sulfate (SDS) with an RB activity equal to that of intact WBM was with the 20% acetone protein fraction. The 60 and 80% fractions were inactive. Combining the 20 with 80% fractions showed a complete inhibition of RB activity. Complete RB loss was also found when WBM was mixed with the 80% fraction, indicating that WBM has both an enzyme system and a factor for regulation of the RB activity in a well controlled metabolic function for the latex RB process.image