bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparative quantitative fatty acid analysis of triacylglycerols using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry and gas chromatography
Authors: Hlongwane C. , Delves I. G. , Wan L. W. , Ayorinde F. O. 
Published: January 2005

AbstractQuantitative analyses of fatty acids from five triacylglycerol products, coconut oil, palm kernel oil, palm oil, lard and cocoa butter, were carried out using two analytical methods: matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) and gas chromatography (GC), in an effort to validate the application of MALDI‐TOFMS in quantitative fatty acid analysis. For the GC analysis, transmethylated products were used, whereas, for the MALDI‐TOF analysis, saponified products were used. Under MALDI‐TOF conditions, the acids were detected as sodiated sodium carboxylates [RCOONa + Na]+ consistent with the mode of ionization that was previously reported.Thus, the MALDI‐TOF mass spectrum of saponified coconut oil showed the presence of sodiated sodium salts of caprylic acid (7.5 ± 0.67, m/z 189), capric acid (6.9 ± 0.83, m/z 217), lauric acid (47.8 ± 0.67, m/z 245), myristic acid (20.4 ± 0.51, m/z 273), palmitic acid (9.8 ± 0.47, m/z 301), linoleic acid (0.9 ± 0.07, m/z 325), oleic acid (4.8 ± 0.42, m/z 327) and stearic acid (2.0 ± 0.13, m/z 329). Saponified palm kernel oil had a fatty acid profile that included caprylic acid (3.5 ± 0.59), capric acid (4.7 ± 0.82), lauric acid (58.6 ± 2.3), myristic acid (20.9 ± 1.5), palmitic acid (7.2 ± 1.1), oleic acid (3.8 ± 0.62) and stearic acid (1.2 ± 0.15). Saponified palm oil gave myristic acid (0.83 ± 0.18), palmitic acid (55.8 ± 1.7), linoleic acid (4.2 ± 0.51), oleic acid (34.5 ± 1.5), stearic acid (3.8 ± 0.26) and arachidic acid (0.80 ± 0.22). Saponified lard showed the presence of myristic acid (1.5 ± 0.24), palmitic acid (28.9 ± 1.3), linoleic acid (13.7 ± 0.67), oleic acid (38.7 ± 1.4), stearic acid (12.8 ± 0.64) and arachidic acid (2.4 ± 0.35). Finally, for saponified cocoa butter, the fatty acid distribution was: palmitic acid (32.3 ± 1.0), linoleic acid (2.6 ± 0.35), oleic acid (34.9 ± 1.7) and stearic acid (30.3 ± 1.6).Quantitative gas chromatographic analysis of the corresponding methyl esters from these triacylglycerol products yielded data that were mostly in agreement with the MALDI‐TOFMS data. The MALDI‐TOF experiment, however, proved to be superior to the GC experiment, particularly with regard to baseline resolution of unsaturated acids. Furthermore, the ability of MALDI‐TOFMS to detect low concentrations of fatty acids rendered it more sensitive than the GC methodology. Copyright © 2001 John Wiley & Sons, Ltd.
A simple and robust conductive graphite coating for sheathless electrospray emitters used in capillary electrophoresis/mass spectrometry
Authors: Nilsson Stefan , Wetterhall Magnus , Bergquist Jonas , Nyholm Leif , Markides Karin E. 
Published: January 2005

AbstractA graphite‐polyimide mixture was used as a conductive coating for sheathless electrospray emitters. The coating procedure described is simple and inexpensive compared to previously described methods. An investigation of the stability of the conductive coating carried out by electrochemical methods revealed good performances during oxidative stress. In addition, no decrease in emitter performance was seen during continuous electrospray in the positive electrospray mode for two weeks. Fast capillary electrophoresis with attomole sensitivity demonstrated the excellent performance of the described sheathless interface when used in conjunction with an orthogonal time‐of‐flight mass spectrometer. The overall simplicity, stability and low cost of this type of sheathless emitter make the described approach highly suitable for any on‐column coupling of low flow rate separation techniques to a mass spectrometer. Copyright © 2001 John Wiley & Sons, Ltd.
Study of mass spectrometric fragmentations of tributyl phosphate via collision‐induced dissociation
Authors: Lesage Denis , Virelizier Henri , Tabet Jean Claude , Jankowski Christopher K. 
Published: January 2005

AbstractTributyl phosphate (TBP) fragmentation mechanisms were studied by mass spectrometry (MS) and tandem mass spectrometry (MS/MS), using electron impact (EI) or chemical (CI) ionisation of the parent compound and its deuterated analogues. The study of this simple compound is essential for the analysis of complex post‐radiolysis mixtures and the identification of particular effects arising from the radiolysis or acid hydrolysis of TBP during nuclear fuel reprocessing. Energy‐resolved mass spectrometry (ERMS) and isotopic labelling helped to establish the fragment ion connectivities by distinct identification of the competitive and consecutive mechanisms. An ion‐dipole intermediate hypothesis, proposed previously in the case of alkyl phosphates and phosphonates in order to explain the mobility of hydrogen atoms from the alkyl chains, is rejected on the basis of the identification of competitive mechanisms in the TBP fragmentation pathways. Copyright © 2001 John Wiley & Sons, Ltd.
Numerical investigation of the effect of electrode size on the behaviour of quadrupole mass filters
Authors: Gibson John Raymond , Taylor Stephen 
Published: January 2005

AbstractThe behaviour of a quadrupole mass spectrometer (QMS) for variation in rod size has been investigated using a numerical approach reported previously. Behaviour is found to vary significantly with the change in rod size and the optimum rod size suggested is closer to that used in some commercial QMS instruments than to the value from analytical approaches. The results allow an upper limit to manufacturing tolerances to be inferred. The present work also confirms that the size of the QMS housing has only a very small effect on QMS behaviour. Copyright © 2001 John Wiley & Sons, Ltd.
A solid phase extraction method for the screening and determination of pyrethroid metabolites and organochlorine pesticides in human urine
Authors: Columé A. , Cárdenas S. , Gallego M. , Valcárcel M. 
Published: January 2005

AbstractA screening method has been developed for the determination of 23 organochlorine pesticides (OCPs) and 3‐pyrethroid metabolities [cis‐ and trans‐3‐(2,2‐dichlorovinyl)‐2,2‐dimethyl‐(1‐cyclopropane) carboxylic acid, cis‐3‐(2,2‐dibromovinyl)‐2,2‐dimethyl‐(1‐cyclopropane) carboxylic acid and 3‐phenoxybenzoic acid] from human urine. OCPs were directly detected in urine samples while pyrethroid metabolites required acid‐induced hydrolysis to convert their conjugates into free acids; all compounds were then cleaned‐up/preconcentrated using solid phase extraction. Determination and quantitation was achieved by gas chromatography with a mass spectrometer detector operating in selected ion monitoring mode. Limits of detection varied between 0.1 and 0.3 ng/mL with linear ranges from 0.3 to 700 ng/mL; the precision of the method was high (4.3–7.2%). Recoveries of all analytes from urine samples fortified at levels of 30 ng/mL for each OCP and 15 ng/mL for each pyrethroid metabolite ranged from 88 to 101% (captan gave the lowest recovery). The results obtained from the analysis of real urine samples show the suitability of the proposed method for monitoring people exposed to organochlorine and pyrethroid pesticides. Copyright © 2001 John Wiley & Sons, Ltd.
High‐sensitivity negative‐ion laser spray for liquid chromatography/mass spectrometry
Authors: Hiraoka Kenzo , Asakawa Yoshiki , Yamamoto Yasuteru , Nakamura Masana , Ueda Kazuhiro 
Published: January 2005

AbstractA negative‐ion mode laser spray interface for use in liquid chromatography/mass spectrometry (LC/MS) has been developed and investigated. The laser spray gave sensitivities that were orders of magnitude better than the negative‐ion electrospray for all samples investigated with the exception of sugars. Fragment ions, HSO4− and SO3−, were formed from the laser‐sprayed aqueous solution of cholesterol 3‐sulfate sodium salt. This suggests that structural information may be obtained directly from the laser‐spray mass spectra for thermally labile compounds. Copyright © 2001 John Wiley & Sons, Ltd.
A novel multifunctional labeling reagent for enhanced protein characterization with mass spectrometry
Authors: Peters Eric C. , Horn David M. , Tully David C. , Brock Ansgar 
Published: January 2005

AbstractIndividual peptides with lysine at the C‐terminus as well as protein tryptic digests were reacted with 2‐methoxy‐4,5‐dihydro‐1H‐imidazole, converting lysine residues to their 4,5‐dihydro‐1H‐imidazol‐2‐yl derivatives. The mass spectra of derivatized digests exhibit a greater number of more intense features than their underivatized counterparts, thus increasing the information obtained in peptide mapping experiments. Additionally, MS/MS spectra of the derivatized peptides are greatly simplified in comparison to their native species, yielding primarily an easily interpretable series of y‐ions. Finally, this novel label also enables differential quantitation studies, as a stable isotopic form containing four deuterium atoms can readily be produced. Copyright © 2001 John Wiley & Sons, Ltd.
Stabilization of invariant sets for nonlinear systems with applications to control of oscillations
Authors: Shiriaev Anton S. , Fradkov Alexander L. 
Published: January 2005

AbstractThe existing results on stabilization of invariant sets for nonlinear systems based on speed–gradient method and the notion ofV‐detectability are overviewed and extended. Applications to control of oscillations in pendulum, cart–pendulum and spherical pendulum systems are presented. Copyright © 2001 John Wiley & Sons, Ltd.
Robust stability and structured uncertainty bounded by the Euclidean norm
Authors: Álamo Teodoro , Dormido Sebastian 
Published: January 2005

AbstractIn the context of robust stability, theμ‐problem is generalized for uncertainty bounded by means of the Euclidean norm. In some cases, a weighted Euclidean norm may be preferable to the infinite norm, for example, when the deviation from the nominal parameters exhibits a Gaussian distribution, also in the case that the parameters of the system are estimated by the ellipsoid algorithm. Several polynomial‐time upper bounds for the newμ‐problem are proposed. Copyright © 2001 John Wiley & Sons, Ltd.
A comparison of small gain versus Lyapunov type robust stability bounds
Authors: Chen Jie , Ren Zhang 
Published: January 2005

AbstractWe address stability issues pertaining to perturbed linear time‐invariant systems described by state space models. We show that for a class of highly structured uncertainties in the system matrix, a robust stability bound given by the complex structured singular value is less conservative than that obtained via Lyapunov approach. This result thus provides a counterpart to an earlier one pertaining to unstructured uncertainties, and serves to extend and support the statement that frequency domain small gain conditions may often be less conservative than those time domain criteria obtained using Lyapunov approach. Copyright © 2001 John Wiley & Sons, Ltd.
Exotic and native vegetation establishment following channelization of a western Iberian river
Authors: Aguiar F.C. , Ferreira M.T. , Moreira I. 
Published: January 2005

AbstractChannelization is often a major cause of human impacts on river systems. It affects both hydrogeomorphic features and habitat characteristics and potentially impacts riverine flora and fauna. Human‐disturbed fluvial ecosystems also appear to be particularly vulnerable to exotic plant establishment. Following a 12‐year recovery period, the distribution, composition and cover of both exotic and native plant species were studied along a Portuguese lowland river segment, which had been subjected to resectioning, straightening and two‐stage bank reinforcement, and were compared with those of a nearby, less impacted segment. The species distribution was also related to environmental data. Species richness and floristic composition in the channelized river segment were found to be similar to those at the more ‘natural’ river sites. Floral differences were primarily consistent with the dominance of cover by certain species. However, there were significant differences in exotic and native species richness and cover between the ‘natural’ corridor and the channelized segment, which was more susceptible to invasion by exotic perennialtaxa, such asEryngium pandanifolium,Paspalum paspalodes,Tradescantia fluminensisandAcacia dealbata. Factorial and canonical correspondence analyses revealed considerable patchiness in the distribution of species assemblages. The latter were associated with small differences in substrate composition and their own relative position across the banks and along the river segments in question. Data was also subjected to an unweighted pair‐group arithmetic average clustering, and the Indicator Value methodology was applied to selected cluster noda in order to obtain significant indicator species. Copyright © 2001 John Wiley & Sons, Ltd.
Sediment deposition along the channel margins of a reach of the middle River Severn, UK
Authors: Steiger J. , Gurnell A.M. , Petts G.E. 
Published: January 2005

AbstractThis paper investigates vegetational, hydrological and geomorphological influences on sedimentation within the river margin of a 1.7 km, sinuous reach of the River Severn, UK. The empirical study was designed to investigate the impact of the following factors on riparian zone sediment deposition: (i) land use, (ii) channel planform location, (iii) the flood stage at which inundation occurs, (iv) submersion time, (v) flood event timing and ordering. Sedimentation was observed using sediment traps located on 48 sample plots within four sites (one on pasture, one within a poplar plantation and two within mixed riparian woodland) during four flood events. A total of 177 observations of sediment deposition were analysed for total dry weight of sediment, particle size and organic content. All sample plots were located within a 30 m wide ribbon of the riparian zone, immediately above the limit of perennial vegetation (i.e. the edge of the low flow channel). Patterns and rates of sedimentation differed between flood events. Whilst significant differences were found in sedimentation between the four sample sites, these were interpreted to be more a function of planform location than land use. The most marked variations were found in the quantity, particle size and organic content of deposited sediment according to riparian zone cross‐sectional morphology and elevation. Highest sedimentation occurred within a 1 m elevation band that correlated with the channel‐ward face of a morphological bench. Percentage sand content of deposited sediment exhibited a change from approximately 35% in a band extending from the low flow channel to a 1 m elevation above the morphological bench edge to approximately 10% above this level. Organic matter content was low (less than 5%) in sediment deposited up to a 1 m elevation above the edge of the morphological bench. Above this level, there was a gradual increase in organic matter content. These observations suggest a link between the form of the riparian zone and the sedimentation process. The relative influence of vegetational, hydrological and geomorphological influences on sedimentation characteristics are also discussed. Copyright © 2001 John Wiley & Sons, Ltd.
Understanding natural patterns and processes in river corridors as the basis for effective river restoration
Authors: Ward J.V. , Tockner K. , Uehlinger U. , Malard F. 
Published: January 2005

Abstract
An Erratum has been published for this article in Regulated Rivers: Research and Management 17 (6) 2001, 311–323.Running water ecology is a young science, the conceptual foundations of which were derived largely from research conducted in Europe and North America. However, virtually all European river corridors were substantially regulated well before the science of river ecology developed. While regulation of North American river systems occurred later than in European systems, river ecology also developed later. Therefore, there is a general impression of rivers as being much less heterogeneous and much more stable than they actually are in the natural state. The thesis of this paper is that established research and management concepts may fail to fully recognize the crucial roles of habitat heterogeneity and fluvial dynamics owing to a lack of fundamental knowledge of the structural and functional features of morphologically intact river corridors. Until quite recently, most concepts in river ecology were based on the implicit assumption that rivers are stable, single‐thread channels isolated from adjacent floodplains. Unfortunately, many rivers are in just such a state, but it should be recognized that this is not the natural condition. This incomplete understanding constrains scientific advances in river ecology and renders management and restoration initiatives less effective. Examples are given of the high level of spatio‐temporal heterogeneity that may be attained in rivers where natural processes still operate on a large scale. The objective of this paper is to promulgate a broader and more integrative understanding of natural processes in river corridors as a necessary prelude to effective river conservation and management. Copyright © 2001 John Wiley & Sons, Ltd.
Cannibalism governing mortality of juvenile brown trout,Salmo trutta, in a regulated stream
Authors: Vik Jon Olav , Borgstrøm Reidar , Skaala Øystein 
Published: January 2005

AbstractAlthough lake‐dwelling trout frequently eat smaller conspecifics in the absence of other fish prey, there are fewer reports of cannibalism in stream populations. However, a coarse riverbed structure and low discharge may facilitate cannibalism by providing pools for large fish whilst limiting refuges for small ones.We estimated the autumn size structure and density of the seatrout population in a regulated stream in western Norway over a period of 12 years. Bioenergetics models were used to relate energy intake in large trout (≥17 cm) to the biomass of small fish present.The number of 0+ trout in autumn decreased with increasing abundance of large trout (log‐log regression, nonlinearR2=0.80,n=10,p=0.0005). The size distribution of 0+ trout in autumn had a lower mean, but more positive skewness, when many small fish were present. Twenty percent of the large trout sampled had parr of trout or salmonSalmo salarin their stomach. The total food consumption estimated for large trout exceeded the total energy content of small fish in years with few small per large trout.We conclude that cannibalism appears to be an important cause of small‐fish mortality in this stream, regulating the abundance and size distribution of small trout. In streams with low discharge, weir building can improve conditions for large trout, presumably reducing the density of small fish. However, it is difficult to predict the net effect on smolt production of improved growth but increased mortality. Copyright © 2001 John Wiley & Sons, Ltd.
Macroinvertebrate instream flow studies after 20 years: a role in stream management and restoration
Authors: Gore James A. , Layzer James B. , Mead Jim 
Published: January 2005

AbstractOver the past two decades of refinement and application of instream flow evaluations, we have examined the hydraulic habitat of aquatic macroinvertebrates in a variety of conditions, along with the role of these macroinvertebrates in sustaining ecosystem integrity. Instream flow analyses assume that predictable changes in channel flow characteristics can, in turn, be used to predict the change in the density or distribution of lotic species or, more appropriately, the availability of useable habitat for those species. Five major hydraulic conditions most affect the distribution and ecological success of lotic biota: suspended load, bedload movement, and water column effects, such as turbulence, velocity profile, and substratum interactions (near‐bed hydraulics). The interactions of these hydraulic conditions upon the morphology and behavior of the individual organisms govern the distribution of aquatic biota. Historically, management decisions employing the Physical Habitat Simulation (PHABSIM) have focused upon prediction of available habitat for life stages of target fish species. Regulatory agencies have rarely included evaluation of benthos for flow reservations. Although ‘taxonomic discomfort’ may be cited for the reluctant use or creation of benthic criteria, we suggest that a basic misunderstanding of the links between benthic macroinvertebrate and the fish communities is still a problem. This is derived from the lack of a perceived ‘value’ that can be assigned to macroinvertebrate species. With the exception of endangered mussel species (for which PHABSIM analysis is probably inappropriate), this is understandable. However, it appears that there is a greater ability to predict macroinvertebrate distribution (that is, a response to the change in habitat quality or location) and diversity without complex population models. Also, habitat suitability criteria for water quality indicator taxa (Ephemeroptera, Plecoptera, and Trichoptera; the so‐called ‘EPTs’) may also provide additional management options to stream regulators. The greatest application for macroinvertebrate criteria will be in low‐order streams where a more immediate link to fish communities can be established. We present an example from Queens Creek, in North Carolina, USA, in which monthly allocations required to preserve the integrity of the benthic macroinvertebrate community were significantly higher than for the target benthic fish species, Cottus bairdi. In the months when both Cottus and community diversity of macroinvertebrates were the ‘bottleneck’ life stages, preservation of only fish species could result in an additional 5–25% loss in macroinvertebrate habitat. We suggest that, as there becomes an increased emphasis on maintaining macroinvertebrates as monitors of stream health, there will be a concurrent emphasis on incorporating hydraulic habitat conditions as a part of bioassessment. Copyright © 2001 John Wiley & Sons, Ltd.
Effects of hydrological regime on the drift algae in a regulated Mediterranean river (River Verdon, southeastern France)
Authors: Bertrand Céline , Siauve Véronique , Fayolle Stéphanie , Cazaubon Arlette 
Published: January 2005

AbstractThe lower part of the River Verdon is profusely regulated by hydroelectric impoundments and the exploitation of canals by the water supply company. This study is an attempt at determining the effects of mean daily flow on the suspended algae in this river. The sampling sectors were localized downstream to the last hydroelectric dam. Two patterns of hydrological regime were analyzed in this hydrosystem: the river manifests a stable and low residual flow and the canal is characterized by a stronger and annually variable flow.In the canal, the algal community has a lower species richness, cell density and diversity than in the river. The abundance of drift algae decreases significantly with the flow. The composition of the algal community also varies in accordance with the flow. The response of drift algae to hydrological regime shows strong seasonal variations; the hydrological disturbance was heavily linked to the freshwater needs. Copyright © 2001 John Wiley & Sons, Ltd.