bluuebunny/crossref_metadata_2025_split huggingface dataset:
Perturbation of ion trajectories by resonant excitation leads to occurrence of ghost peaks
Authors: Favre Amelie , Gonnet Florence , Tabet Jean‐Claude 
Published: August 2002

AbstractWe have shown in a recent paper (Kocher F, Favre A, Gonnet F, Tabet JC J. Mass Spectrom. 1998; 33: 921) that under particular ion trapping conditions, i.e. space charge, artefacts called ghost peaks were displayed in mass spectra and isolation spectra. All experimental factors which modified the space‐charge strength, influenced the intensities of the ghost peaks. It was demonstrated that only the injected ions having qz ≤0.25 (βz ≤ 2/11) at the beginning of the analytical scan step gave rise to the formation of such artefact peaks. In fact, the ion cloud defocused by space charge was subjected to high‐order multipole fields (e.g. 22‐pole, Wang Y, Schubert M, Franzen J, Proc. 44th ASMS Conf. Mass Spectrom. and Allied Topics, Portland OR, 1996; p. 131), so that the trajectories of the analysed ions were destabilized thus affecting the ion ejection which then occurred at qz = 0.908 (βz = 1, natural boundary). However, ions having 0.25 (βz ≤ 2/11) ≤qz ≤0.45 (βz ≤ 1/3), at the beginning of the analytical scan step, were not destabilized, and were correctly ejected where the axial modulation was applied (βz ≤ 1/3). Thus, under extreme space‐charge conditions, the ion excursion increased, the influence of the non‐linear resonance at βz = 2/11 was enhanced, ion excursion was more enhanced, and the ions were not ejected at βz = 1/3 but at βz = 1.We shown here that, again under the influence of the non‐linear resonance at βz = 2/11, under space‐charge conditions the ion excursion increased, and the application of a resonant excitation dramatically enhanced this ion excursion, compared to only the isolation step as was performed in the previous work. This led to these ions not being ejected at βz = 1/3 but rather at βz = 1, and thus being displayed as ghost peaks in the collisionally induced dissociation (CID) spectra. This behavior could take place for other working ejection points, which occur at non‐linear resonances (e.g. βz = 2/11 as well as βz = 2/3). Copyright © 2001 John Wiley & Sons, Ltd.
Combining energy‐dependent electrospray ionisation with tandem mass spectrometry for the analysis of inorganic compounds
Authors: Dyson Paul J. , Hearley Andrew K. , Johnson Brian F. G. , McIndoe J. Scott , Langridge‐Smith Patrick R. R. , Whyte Christopher 
Published: August 2002

AbstractThe recently developed technique of energy‐dependent electrospray ionisation mass spectrometry (EDESI‐MS) has been implemented on a triple quadrupole mass spectrometer such that fragmentation occurs in the collision cell rather than at the skimmer cone. This modification enables a superior two‐dimensional map of the collision voltage versus mass‐to‐charge ratio to be generated, providing unambiguous peak assignments. This latest enhancement to the technique is referred to as energy‐dependent electrospray ionisation tandem mass spectrometry (EDESI‐MS/MS). In the present work the technique has been applied to investigate the sequential removal of ligands from the inorganic mixed‐metal anionic cluster compound [Ru5CoC(CO)16]−, which serves to illustrate the advantages of this approach. Copyright © 2001 John Wiley & Sons, Ltd.
Proteomics of gluten: mapping of subunit 1 Ax2* in Cheyenne cultivar by matrix‐assisted laser desorption/ionization
Authors: Cozzolino Rosaria , Giorgi Sabrina Di , Fisichella Salvatore , Garozzo Domenico , Lafiandra Domenico , Palermo Angela 
Published: August 2002

AbstractThis paper reports results on the verification of the 1Ax2* high molecular weight glutenin subunit sequence in Cheyenne cultivar. The gene sequence of the protein is known but recently some text changes have been made, and furthermore until now no characterization of post‐translational modifications has been reported. The two published sequences, named I and II, differ in four residues at positions 23, 208, 475, and 611. The first sequence contains 20 Arg and 6 Lys residues, producing 26 tryptic fragments, since the Arg109‐Pro110 bond is generally not cleaved by trypsin. The second sequence contains 19 Arg and 6 Lys residues, producing 25 tryptic peptides, again because of the Arg109‐Pro110 bond. Both sequences generate two cyanogen bromide fragments. Matrix‐assisted laser desorption/ionization analysis of the tryptic digest of the high‐MW glutenin subunit 1Ax2* resulted in the identification of 24 out of the 26 expected peptides for sequence I, a sequence coverage of 99.5%. These results were sufficient to rule out sequence II and any protein glycosylation and any other post‐translational modifications to within the detection limits of the method. It was found that the choice of matrix considerably influenced the sequence coverage in peptide mapping. Copyright © 2001 John Wiley & Sons, Ltd.
Atmospheric pressure matrix‐assisted laser desorption/ionization ion trap mass spectrometry of sulfonic acid derivatized tryptic peptides
Authors: Keough T. , Lacey M. P. , Strife R. J. 
Published: August 2002

AbstractAtmospheric pressure matrix‐assisted laser desorption/ionization (AP‐MALDI) and ion trap mass spectrometry have been used to study the fragmentation behavior of native peptides and peptide derivatives prepared for de novo sequencing applications. Sulfonic acid derivatized peptides were observed to fragment more extensively and up to 28 times more efficiently than the corresponding native peptides. Tandem mass spectra of native peptides containing aspartic or glutamic acids are dominated by cleavage on the C‐terminal side of the acidic residues. This significantly limits the amount of sequence information that can be derived from those compounds. The MS/MS spectra of native tryptic peptides containing oxidized Met residues show extensive loss of CH3SOH and little sequence‐specific fragmentation. On the other hand, the tandem mass spectra of derivatized peptides containing Asp, Glu and oxidized Met show much more uniform fragmentation along the peptide backbone. The AP‐MALDI tandem mass spectra of some derivatized peptides were shown to be qualitatively very similar to the corresponding vacuum MALDI postsource decay mass spectra, which were obtained on a reflector time‐of‐flight instrument. However, the ion trap mass spectrometer offers several advantages for peptide sequencing relative to current reflector time‐of‐flight instruments including improved product ion mass measurement accuracy, improved precursor ion selection and MSn. These latter capabilities were demonstrated with solution digests of model proteins and with in‐gel digests of 2D‐gel separated proteins. Copyright © 2001 John Wiley & Sons, Ltd.
Gas‐phase ion/molecule reactions between dimethoxyphosphonium ions and aromatic hydrocarbons
Authors: Leclerc Eric , Buchmann William , Taphanel Marie‐Hélène , Morizur Jean‐Pierre 
Published: August 2002

AbstractIon/molecule reactions between O=P(OCH3)2+ phosphonium ions and six aromatic hydrocarbons (benzene, toluene, 1,2,4‐trimethylbenzene, naphthalene, acenaphthylene and fluorene) were performed in a quadrupole ion trap mass spectrometer. The O=P(OCH3)2+ phosphonium ions, formed by electron impact from neutral trimethyl phosphite, were found to react with aromatic hydrocarbons (ArHs) to give (i) an adduct [ArH, O=P(OCH3)2]+ and (ii) for ArHs which have an ionization energy below or equal to 8.14 eV, a radical cation ArH+· by charge transfer reaction. Collision‐induced dissociation experiments, which produce fragment ions other than the O=P(OCH3)2+ ions, indicate that the adduct ions are covalent species. Isotope‐labeled ArHs were used to elucidate fragmentation mechanisms. The charge transfer reactions were investigated using density functional theory at the B3LYP/6‐311 + G(3df,2p)//B3LYP/6‐31G(d,p) level of theory. The potential energy surface obtained from B3LYP/6‐31G(d,p) calculations for the reaction between O=P(OCH3)2+ and benzene is described. Copyright © 2002 John Wiley & Sons, Ltd.
A QFT framework for nonlinear robust stability
Authors: Baños Alfonso , Barreiro Antonio , Gordillo Francisco , Aracil Javier 
Published: August 2002

AbstractThe problem of deriving conditions for a stabilizing linear compensator in a uncertain nonlinear control system is addressed, for some types of memoryless nonlinearities like the saturation or the dead zone. The approach is to incorporate to QFT conditions given by the application of harmonic balance and multiplier techniques, providing the designer with a very transparent tool for synthesizing nonlinear stabilizing compensators, balancing between different possible alternatives. Copyright © 2002 John Wiley & Sons, Ltd.
Epitaxial phenomena across length and time scales
Authors: Vvedensky D. D. 
Published: August 2002

AbstractThe morphological evolution of an epitaxial film results from atomistic processes such as adatom motion and step–adatom interactions asserting their influence over the macroscopic length and time scales of the growth front. Modelling epitaxial phenomena thus necessitates making a compromise between the detailed information provided by first‐principles methods and the computational flexibility afforded by methods such as Monte‐Carlo simulations and continuum equations of motion, in which atomistic processes are replaced by coarse‐grained effective kinetics. We will review the various approaches that are available for modelling epitaxial phenomena using the (001) surfaces of III–V compound semiconductors as a case study, with a view to making direct comparisons with experimental measurements and to establishing a methodology that is capable of incorporating all pertinent length and time scales. Copyright © 2001 John Wiley & Sons, Ltd.
Correlation coefficient estimation involving a left censored laboratory assay variable
Authors: Lyles Robert H. , Fan Dongjie , Chuachoowong Rutt 
Published: August 2002

AbstractWhen assessing a correlation between two exposure or biological marker variables, one sometimes encounters the problem of indeterminate values for one of the variables due to an assay detection limit. In this event, investigators often report correlation coefficients computed after removing the pairs involving non‐detectable values, or after substituting some small constant for those values. These ad hoc practices can lead to bias in both point and confidence interval estimates of the true correlation coefficient. To address this issue, we consider two parametric techniques for estimating the correlation in the presence of left censoring for one of the variables. The first is a maximum likelihood approach, and the second is an adaptation of multiple imputation motivated primarily by potential benefits in confidence interval coverage. Both of the estimators studied reduce to the standard Pearson's correlation coefficient in the event of no censoring, and hence are valid in cases where this measure would be appropriate for the complete data. We assess these approaches empirically and contrast them with ad hoc methods for estimating the correlation between cervicovaginal human immunodeficiency virus (HIV) viral load measurements and CD4+ lymphocyte counts from HIV positive women enrolled in a clinical trial conducted in Bangkok, Thailand. Copyright © 2001 John Wiley & Sons, Ltd.
Testing abnormality in the spatial arrangement of cells in the corneal endothelium using spatial point processes
Authors: Díaz M. E. , Ayala G. , Quesada S. , Martínez‐Costa L. 
Published: August 2002

AbstractThe study of central corneal endothelium morphology is important in Ophthalmology. Some of the pathologies that could compromise endothelial cell morphology are trauma, cataract, surgery, use of contact lenses, corneal dystrophies or degenerations. The quantitative analysis of cell shape and cellular pattern is more sensitive in detecting subtle changes in endothelial morphology than cell density measurement or cell area analysis. In this paper, the morphology of the central cornea, the most important area from the point of view of vision, is studied through an associated bivariate spatial point pattern: the centroids of the cells and the triple points, that is, the points where three different cells converge. Nine different summary descriptors (widely used in the statistical analysis of spatial point patterns) have been used: the empty space distribution function; the nearest neighbour distribution function and Ripley's 𝒦‐function for each type of point separately (centroids and triple points), plus the corresponding three versions of these functions in the bivariate case. A control sample with similar age and cell density and no known abnormality is associated to each patient. The above descriptors are calculated for the patient and the controls. Each descriptive of the patient is compared with the corresponding descriptors from the controls by means of a graphical analysis and a formal test. Some patients presenting different pathologies are analysed in detail. Endothelia considered morphologically abnormal by visual inspection, which were not detected by hexagonality or density analysis, could be distinguished from control endothelia by these new descriptors. Copyright 2001 John Wiley & Sons, Ltd.
Role of ultrasonography in the staging of gastrointestinal neoplasms
Authors: Neumaier Carlo Emanuele , Cittadini Giuseppe , Grasso Andrea , Dahmane M'hamed 
Published: August 2002

AbstractThis article reviews the capabilities and limits of ultrasonography (US) in the staging of gastrointestinal neoplasms. US is a well‐established tool in the investigation of abdominal diseases. Its role is very important in the first approach to liver, gallbladder, biliary, and pancreatic diseases, but its abilities for accurate staging may be limited by various factors, which will be discussed. In the evaluation of the stomach and intestine, US is rarely utilized, but it can occasionally demonstrate an unsuspected gastrointestinal mass that usually must be evaluated further with specific techniques (endoscopy and barium studies) to confirm the diagnosis and to perform an accurate staging (with endosonography and computed tomography). Semin. Surg. Oncol. 20:86–90, 2001. © 2001 Wiley‐Liss, Inc.
Role of the surgeon as a variable in the treatment of rectal cancer
Authors: Hermanek Paul , MD Peter J. Hermanek, 
Published: August 2002

AbstractIncreasingly, data are being accumulated on the influence of intersurgeon variability on outcome after curative surgical treatment of rectal carcinoma. Thus, today the individual surgeon has to be considered as an independent factor influencing locoregional recurrence, as well as survival rates. In general, higher local control and survival can be expected for specialized colorectal surgeons. There are no clear correlations between surgical volume and outcome. Interinstitutional variability in treatment results reflects intersurgeon variability, but analysis is generally more difficult because of a lack of homogeneity with respect to different confounding factors. There are several factors in surgical technique that are important for long‐term outcome. Of greatest apparent importance is the adequacy of mesorectal excision (for carcinomas of the middle and lower third, total mesorectal excision; for carcinomas of the upper third, mesorectal excision down to a mesorectal plane 5 cm distal to the gross tumor margin detected by the surgeon in situ). Furthermore, intraoperative local tumor spillage (tumor perforation during mobilization, incision into the tumor), en bloc resection technique, skill, and the extent of regional lymphadenectomy may influence outcome. For quality assurance, detailed operative reports are required, as well as histopathology examinations concerning indicators of surgical oncologic quality discernable from the resection specimens. In future clinical trials of multimodal treatment of rectal cancer, quality assurance of surgery and pathology is necessary for consideration of the surgeon and surgical technique prognostic factors. Semin. Surg. Oncol. 19:329–335, 2000. © 2000 Wiley‐Liss, Inc.
Decreased calcineurin and increased phosphothreonine‐DARPP‐32 in the striatum of rats behaviorally sensitized to methamphetamine
Authors: Lin Xian‐Hao , Hashimoto Takeshi , Kitamura Noboru , Murakami Naoya , Shirakawa Osamu , Maeda Kiyoshi 
Published: August 2002

AbstractWe investigated changes in signal transduction via calcineurin (CaN) in the striatum of rats behaviorally sensitized to methamphetamine (Meth). The rats were injected with Meth (4 mg/kg, s.c.) five times a week for 3 weeks and then were given a challenge dose of Meth (2 mg/kg, s.c.). Seven days after the challenge test, we determined the levels of CaN Aα and Aβ by Western blotting. We further immunoquantified DARPP‐32 (dopamine‐ and cAMP‐regulated phosphoprotein, mw 32,000) and phosphothreonine‐DARPP‐32, which can be dephosphorylated at threonine sites by CaN. We found that both CaN Aα and Aβ were significantly decreased in the particulate fractions but were not changed in the soluble fractions from the striatum of Meth‐sensitized rats as compared with control rats. The same findings were observed in the striatum of rats 6 h after the injection of PCP (10 mg/kg, s.c.). In the striatum of Meth‐sensitized rats, phosphothreonine‐DARPP‐32 immunoreactivities significantly increased, but DARPP‐32 immunoreactivities were not significantly different from those of the control rats. These results indicate that the activity of signal transduction via CaN is functionally decreased in the striatum of Meth‐sensitized rats. Synapse 44:181–187, 2002. © 2002 Wiley‐Liss, Inc.
Comparison of paired‐pulse facilitation of AMPA and NMDA synaptic currents in the lateral amygdala
Authors: Zinebi Fatiha , Russell Rex T. , McKernan Margaret , Shinnick‐Gallagher Patricia 
Published: August 2002

AbstractStimulating thalamic fibers exiting from the internal capsule evokes a glutamatergic excitatory postsynaptic current (EPSC) recorded in vitro with patch electrodes in neurons of the rat lateral amygdala (LA). The purpose of this study is to compare paired‐pulse facilitation (PPF), a form of short‐term synaptic plasticity, of AMPA and NMDA receptor‐mediated EPSCs. Analysis of PPF at this synapse is important since, in fear‐conditioned animals, PPF reflects an enhanced transmitter release but the amplitude of only AMPA EPSCs is facilitated. PPF magnitude of the composite EPSC is a result of both AMPA and NMDA receptor activation; however, the characteristics of AMPA and NMDA PPF are dissimilar. Specifically, the NMDA EPSC shows greater PPF (NMDA PPF) than does the AMPA EPSC whether measuring the NMDA PPF magnitude in an AMPA antagonist/Mg2+‐free solution or by subtracting the AMPA EPSC from the composite EPSC in normal Mg2+. Presynaptic NMDA receptors neither influence AMPA PPF nor account for the difference between the NMDA and AMPA PPF. Another difference was that removal of inhibitory tone enhanced AMPA PPF, while it had mixed effects on NMDA PPF. Furthermore, AMPA PPF was independent of stimulus intensity and postsynaptic voltage, unlike the NMDA PPF. Another dissimilarity was that the amplitudes of pairs of AMPA EPSCs were not correlated, suggesting presynaptic mechanisms. In contrast, NMDA PPF was dependent on stimulus intensity and postsynaptic voltage and the amplitudes of paired NMDA EPSCs had a positive correlation, suggesting a postsynaptic influence. Both AMPA and NMDA PPF were influenced by GABA inhibition and this could be a factor in the magnitude disparity. These data show that AMPA and NMDA PPF have different characteristics and contribute to the composite PPF in the thalamic to lateral amygdala pathway. Synapse 42:115–127, 2001. © 2001 Wiley‐Liss, Inc.
Methylenetetrahydrofolate reductase: A common human polymorphism and its biochemical implications
Authors: Matthews Rowena G. 
Published: August 2002

AbstractMethlenetetrahydrofolate (CH2‐H4folate) is required for the conversion of homocysteine to methionine and of dUMP to dTMP in support of DNA synthesis, and also serves as a major source of one carbon unit for purine biosynthesis. This review presents biochemical studies of a human polymorphism in methylenetetrahydrofolate reductase, which catalyzes the reaction shown below. The mutation decreases the flux of CH2‐H4folate into CH3‐H4folate, and is associated with both beneficial and deleterious effects that can be traced to the molecular effect of the substitution of alanine 222 by valine. © 2002 The Japan Chemical Journal Forum and John Wiley & Sons, Inc. Chem Rec 2: 4–12, 2002
EDXRF and TXRF analysis of aerosol particles and the mobile fraction of soil in Botswana
Authors: Chimidza Samuel , Viksna Arturs , Selin Lindgren Eva 
Published: August 2002

AbstractSurface soil and airborne particles were sampled at two locations in Botswana, Serowe and Gaborone. EDXRF and TXRF were used to analyse the soil samples for elemental concentrations and the mobile (bio‐available) fractions of the soil. EDXRF was also used for analysis of the aerosol particles in two size fractions, PM2.5 and PM2.5–10. To extract the mobile fraction, the soil samples were leached in ammonium acetate solution at pH 7. Most of the elements in the soils were found to have very low mobility at the two locations. In order to identify elements for which the major sources in the fine and coarse airborne particles are anthropogenic, elemental concentrations in the soil were used to calculate enrichment factors of airborne particles with respect to titanium in soil. From the calculated enrichment factors, it appears that the elements attributed to bio‐mass burning and those attributed to car exhausts have strong anthropogenic sources in Serowe and Gaborone, respectively. Copyright © 2001 John Wiley & Sons, Ltd.
Specifying and Refining Internal Operations in Z
Authors: Derrick John , Boiten Eerke , Bowman Howard , Steen Maarten 
Published: August 2002

Abstract.
An important aspect in the specification of distributed systems is the
role of the internal (or unobservable) operation. Such operations are not part of the interface to the environment (i.e. the user cannot invoke them), however, they are essential to our understanding and correct modelling of the system. In this paper we are interested in the use of the formal specification notation Z for the description of distributed systems. Various conventions have been employed to model internal operations when specifying such systems in Z. If internal operations are distinguished in the specification notation, then refinement needs to deal with internal operations in appropriate ways.
Using an example of a telecommunications protocol we show that standard Z refinement is inappropriate for refining a system when internal operations are specified explicitly. We present a generalisation of Z refinement, called weak refinement, which treats internal operations differently from observable operations when refining a system. We discuss the role of internal operations in a Z specification, and in particular whether an equivalent specification not containing internal operations can be found. The nature of divergence through livelock is also discussed.
Case Study in Protocol Validation: Validating an ATM Signalling Protocol
Authors: Vassiliou-Gioles Theofanis , Schieferdecker Ina 
Published: August 2002

Abstract.
This paper discusses validation techniques for communication protocols and analyzes the practical use of selected validation techniques in an automated manner. A case study on validating the ATM (Asynchronous Transfer Mode) Signalling Protocol as specified by ITU-T in Q.2931 is used for this analysis. Different error classes are identified and validated. An assessment of the different validation techniques in terms of effort and quality of results is given. As a result of the case study, an evaluation of the Q.2931 SDL specification completes the paper.