bluuebunny/crossref_metadata_2025_split huggingface dataset:
Elemental maps from EFTEM images using two different background subtraction models
Authors: Quintana C. , Lechaire J.P. , Bonnet N. , Risco C. , Carrascosa J.L. 
Published: August 2002

AbstractAcquisition of a great number of energy‐filtered images in a TEM (EFTEM) around the characteristic signal with a low energy‐selecting slit allows display of the electron energy loss (EEL)‐spectrum of regions of interest (ROIs) of a sample. These EEL‐spectra can be submitted to the different treatments already in use for electron energy loss spectroscopy (EELS). In particular, it is possible to fit the experimental background with different mathematical models, using images acquired below and above a characteristic ionization edge. After this fitting, elemental maps can be computed by subtraction of the extrapolated/interpolated background from the characteristic images. In this work, we compared two mathematical models for background fitting—the Egerton power law and the log‐polynomial law. We studied the low‐energy region (40–150 eV) and a higher‐energy region (350–600 eV) with the aid of software for interactive processing of EFTEM image series that we developed. The analyzed elements were the constitutive elements: iron, phosphorus, nitrogen, and oxygen in several biological materials. Two analytical TEMs, one equipped with a post‐column and the other with an in‐column spectrometer, were used. Our experimental results confirm that the power law is very sensitive to the value of the energy loss of the pre‐edge images when the background is computed by extrapolation. The log‐polynomial model is less sensitive than the power law model to the value of the energy loss of the pre‐edge images in the low energy region. For the oxygen K edge at 535 eV, it gives the best fit when it is combined with the interpolation method. The use of programs that facilitate the handling of EFTEM image series, and the controlled calculation of the background under the characteristic images, represent a step forward in the generation of elemental maps. Microsc. Res. Tech. 53:147–156, 2001. © 2001 Wiley‐Liss, Inc.
Gastric leptin
Authors: Lewin Miguel J.M. , Bado André 
Published: August 2002

AbstractThe recent discovery of gastric leptin has initiated several investigations on the possible role of leptin in digestive physiology. The following clues are currently suggested: leptin might control meal size in cooperation with Cholecystokinin, help cytoprotection of the gastric mucosa, play a role in gut inflammatory processes, regulate secretion of gastric hormones such as gastrin and somatostatin, and modulate intestinal transport of small peptides. The present review is a brief survey of the most significant advances in these issues. Microsc. Res. Tech. 53:372–376, 2001. © 2001 Wiley‐Liss, Inc.
Comparative analysis of adrenomedullin‐like immunoreactivity in the hypothalamus of amphibians
Authors: Muñoz Margarita , López Jesús M. , Sánchez‐Camacho Cristina , Moreno Nerea , Crespo Miguel , González Agustín 
Published: August 2002

AbstractAdrenomedullin (AM) is a novel neuropeptide with special significance in the mammalian hypothalamo‐hypophysial axis. By using an antiserum specific for human AM, we have studied the localization of AM‐like immunoreactive (AMi) cell bodies and fibers in the hypothalamus and hypophysis of the amphibians Rana perezi (anuran), Pleurodeles waltl (urodele), and Dermophis mexicanus (gymnophionan). Distinct AMi cell groups were found for each species. In the anuran, six cell groups were localized in the preoptic and infundibular regions, whereas only three and one were found in the urodele and gymnophionan, respectively. A comparative analysis of AMi cells and cells expressing arginine vasotocin (AVT), neuropeptide Y (NPY), and tyrosine hydroxylase (TH) revealed strong differences between species. Thus, colocalization of AVT/AM is most likely to occur in the preoptic magnocellular nucleus of urodeles and it is reflected by the intense AM immunoreactivity in the neural lobe of the hypophysis. Colocalization of NPY/AM seems to be possible in the suprachiasmatic nucleus of anurans. In the gymnophionan, cells containing AVT and NPY are distinct from AMi cells. Only in anurans, the ventral aspect of the suprachiasmatic nucleus possesses a small population of AMi cells that express also TH immunoreactivity and most likely also express NPY. The results strongly suggest that AM in amphibians plays an important regulatory role in the hypothalamo‐hypophysial system, as has been demonstrated in mammals. On the other hand, substantial differences have been found between species with respect to the degree of colocalization with other chemical substances. Microsc. Res. Tech. 54:173–187, 2001. © 2001 Wiley‐Liss, Inc.
On the critical point‐arboricity graphs
Authors: Škrekovski Riste 
Published: August 2002

AbstractIn this paper, we study the critical point‐arboricity graphs. We prove two lower bounds for the number of edges of k‐critical point‐arboricity graphs. A theorem of Kronk is extended by proving that the point‐arboricity of a graph G embedded on a surface S with Euler genus g = 2, 5, 6 or g ≥ 10 is at most $k =\lfloor {9 +\sqrt {1+ 24\, g}\over 4}\rfloor$ with equality holding iff G contains either K2k−1 or K2k−4 + C5 as a subgraph. It is also proved that locally planar graphs have point‐arboricity  ≤ 3 and that triangle‐free locally planar‐graphs have point‐arboricity ≤ 2. © 2002 John Wiley & Sons, Inc. J Graph Theory 39: 50–61, 2002
A rigid graph for every set
Authors: Nešetřil Jaroslav 
Published: August 2002

AbstractA graph G is called rigid if the identical mapping V(G)→V(G) is the only homomorphism G→G. In this note we give a simple construction of a rigid oriented graph on every set. © 2002 John Wiley & Sons, Inc. J Graph Theory 39: 108–110, 2002
Stability of arc‐transitive graphs
Authors: Surowski David B. 
Published: August 2002

AbstractThe present paper investigates arc‐transtive graphs in terms of their stability, and shows, somewhat contrary to expectations, that the property of instability is not as rare as previously thought. Until quite recently, the only known example of a finite, arc‐transitive vertex‐determining unstable graph was the underlying graph of the dodecahedron. This paper illustrates some methods for constructing finite arc‐transitive unstable graphs, and three infinite families of such graphs are given as applications. © 2001 John Wiley & Sons, Inc. J Graph Theory 38: 95–110, 2001
Perceptions of drudgery in agricultural and animal husbandry operations: a gender analysis from Haryana State, India
Authors: Thakur Sonika , Varma Shashi Kanta , Goldey Patricia A. 
Published: August 2002

AbstractThe paper examines the involvement and drudgery profile of rural women and men in agricultural and animal husbandry activities in India. The activities assigned to men were those which were considered to demand greater physical power, skill and performance. The activities assigned to women were considered to demand less physical power, lower skill and more time. They were also monotonous in their nature and low paid. The implications of the study indicate a need to match technological and innovative solutions to the drudgery that women experience in agricultural and animal husbandry operations: also, the fact that women shoulder a greater share of those tasks perceived to involve drudgery is in itself worthy of particular attention. In addition to shouldering almost the entire work load of household activities and substantial responsibilities in child rearing, women were found to work in agricultural and animal husbandry activities for more hours than men. Copyright © 2001 John Wiley & Sons, Ltd.
Operating principle of an electron monochromator in an axial magnetic field
Authors: Grill Verena , Drexel Herwig , Sailer Wolfgang , Lezius Matthias , Märk Tilmann D. 
Published: August 2002

AbstractElectron monochromators which are operated within an axial magnetic (guiding) field are especially suitable for the production of monochromatic electrons at low energies. Although in principle the technology of such devices has an appreciable historic background, we have discovered experimentally important new features, which cannot be understood using the previously published theories of operation. An in‐depth study of the electron trajectories in a crossed electric and magnetic field using Simion1 showed a number of possible pitfalls, which have to be avoided in construction and operation. From our simulations we derived a novel design and operational method, which is currently under evaluation. We have already demonstrated that using this novel design an electron energy resolution of about 50 meV is realistic. Copyright © 2001 John Wiley & Sons, Ltd.
Characterization of novel di‐ and tricarboxylic acids in fine tropical aerosols
Authors: Zdráhal Zbyněk , Vermeylen Reinhilde , Claeys Magda , Maenhaut Willy , Guyon Pascal , Artaxo Paulo 
Published: August 2002

AbstractThree unknown di‐ and tricarboxylic acids were characterized in the fine size fraction of aerosols which were collected during the wet season in the Amazon basin (Rondonia, Brazil). For the structural characterization of the methyl esters of these unknown compounds, mass spectrometry with electron ionization (EI) and tandem mass spectral techniques combined with gas chromatographic (GC) separation were employed. Fragment and parent ion spectra were recorded during elution of the GC peaks by linked scanning of the B and E sectors in combination with high‐energy collision‐induced dissociation. The fragmentation patterns of significant ions in the first‐order EI spectra were also obtained for nonanedioic acid, which was examined as a model compound. The compounds were tentatively identified as 4‐acetyloxyheptanedioic acid and cis and trans isomers of 5‐hexene‐1,1,6‐tricarboxylic acid. Since there were indications of biomass burning during the aerosol sampling the di‐ and tricarboxylic acids characterized in the present work could be markers for biomass burning. Furthermore, the characterization of di‐ and tricarboxylic acids in the fine size fraction of atmospheric aerosols may be important for assessing the effects of organic aerosols in cloud formation. Copyright © 2001 John Wiley & Sons, Ltd.
Field desorption mass spectrometry of large multiply branched saturated Hydrocarbons
Authors: Gross Jürgen H. , Vékey Károly , Dallos András 
Published: August 2002

AbstractLarge multiply branched saturated hydrocarbons containing 67–103 carbon atoms (molecular masses 941.8–1446.8 Da) were analyzed by field desorption mass spectrometry (FD‐MS) with a double‐focusing mass spectrometer. FD‐MS was found to have detection limits in the 100 fmol range. The FD mass spectra exhibited molecular ions of astonishingly low abundance. However, the fragment ions formed were closely related to the proposed molecular structure, allowing us to set up rules for straightforward structure elucidation of unknowns. In detail, (i) dehydrogenation, (ii) alkyl losses from molecular ions and (iii) subsequent alkene losses were observed. The influence of the electric field strength on dehydrogenation and C—C cleavages was examined by variation of the emitter potential. Additionally, ion dissociations in the ion source and in the first and second field‐free regions, respectively, were compared to study the relative importance of field‐induced and thermally induced processes. Copyright © 2001 John Wiley & Sons, Ltd.
Mass spectrometry and combinatorial chemistry: a short outline
Authors: Triolo Antonio , Altamura Maria , Cardinali Franco , Sisto Alessandro , Maggi Carlo Alberto 
Published: August 2002

AbstractThe rapid evolution of combinatorial chemistry in recent years has led to a dramatic improvement in synthetic capabilities. The goal is to accelerate the discovery of molecules showing affinity against a target, such as an enzyme or a receptor, through the simultaneous synthesis of a great number of structurally diverse compounds. This is done by generating combinatorial libraries containing as many as hundreds or thousands of compounds. The need to test all these compounds led to the development of high‐throughput screening (HTS) techniques, and also high‐throughput analytical techniques capable of assessing the occurrence, structure and purity of the products. In order to be applied effectively to the characterization of combinatorial libraries, an analytical technique must be adequately sensitive (to analyse samples which are typically produced in nanomole amounts or less), fast, affordable and easy to automate (to minimize analysis time and operator intervention). Although no method alone can meet all the analytical challenges underlying this task, the recent progress in mass spectrometric (MS) instrumentation renders this technique an essential tool for scientists working in this area.We describe here relevant aspects of the use of MS in combinatorial technologies, such as current methods of characterization, purification and screening of libraries. Some examples from our laboratory deal with the analysis of pooled oligomeric libraries containing n × 324(n = 1, 2) compounds, using both on‐line high‐performance liquid chromatography/MS with an ion trap mass spectrometer, and direct infusion into a triple quadrupole instrument. In the first approach, MS and product ion MS/MS with automatic selection of the precursor were performed in one run, allowing library confirmation and structural elucidation of unexpected by‐products. The second approach used MS scans to characterize the entire library and also precursor ion and neutral loss scans to detect selectively components with given structural characteristics. Copyright © 2001 John Wiley & Sons, Ltd.
Investigation of homo‐ and heterodimer alkali metal cation complexes of resorc[4]arenes by electrospray ionization mass spectrometry
Authors: Letzel Matthias C. , Agena Ceno , Mattay Jochen 
Published: August 2002

AbstractResorc[4]arenes are compounds with interesting properties, mainly because of their ability to form host–guest complexes with the guest located inside the cavity. The size of the guest limits the complexation, as shown by a competition experiment with tetraalkylammonium ions of different size. By electroscopy ionization tandem mass spectrometric experiments on resorc[4]arene heterodimers bearing an alkali metal ion as guest, it was found that there must be two different binding mechanisms for alkali metal ions with high surface charge density (Li+ and Na+) on the one hand compared with those with a lower surface charge density on the other hand (K+, Rb+, Cs+). Copyright © 2001 John Wiley & Sons, Ltd.
Occurrence and severity of infections caused by subgroup A and B respiratory syncytial virus in children in Southeast Brazil
Authors: Cintra O.A.L. , Owa M.A. , Machado A.A. , Cervi M.C. , Figueiredo L.T.M. , Rocha G.M. , Siqueira M.M. , Arruda E. 
Published: August 2002

AbstractThe frequency and severity of infections caused by respiratory syncytial virus (RSV) were assessed in children <2 years of age seen at the emergency department. The frequency of RSV detection in the clinical virology laboratory during the past 3 years was also analyzed retrospectively. RSV was found in 21.6% (188/869) of the samples collected from children seen at the emergency department and was found to be more frequent during the autumn, being less frequent or negligible by midwinter. RSV subgroups A and B co‐circulated within the same time period in children seen at the emergency department, with varying predominance of either subgroup. There was no significant association of RSV subgroup with disease severity, but only a trend for RSV subgroup B being more frequent in children with risk factors for severe disease. J. Med. Virol. 65:408–412, 2001. © 2001 Wiley‐Liss, Inc.
Video‐microscopic analysis of dye coupling in the salamander olfactory bulb
Authors: Du J. , Maloney R.E. , Hamilton K.A. 
Published: August 2002

AbstractCells in the mitral cell (MCL) and granule cell (GCL) layers of the olfactory bulb shape the representation of odor information in the brain. After intracellular Lucifer Yellow (LY) injections into lightly fixed olfactory bulb slices, clusters of dye coupled cells were previously observed in the MCL and GCL, but the relative extent of coupling in the two layers was unknown in adults. In the present study, the time course of LY coupling in the adult salamander olfactory bulb was quantified using video‐microscopic methods. Analysis of fluorescent cell body counts showed that the incidence and the extent of LY coupling are greater in the GCL than in the MCL. With optimal low‐current injection procedures, 97% of the injections into the GCL exhibited at least one coupled cell, and on average groups of six to eight cells were counted. Fewer injections into the MCL exhibited only one to three coupled cells. Some of these coupled cells were clearly mitral cells. No staining of cells was observed after extracellular LY injections, and intracellular injections of dextran dyes stained single cells, providing evidence that the LY coupled cells were stained through an intercellular route, presumably gap junctions. In live intact preparations, rapid LY staining of cell clusters was also observed using patch pipettes. Together, these results provide evidence that robust coupling occurs among olfactory bulb neurons in adults, which could have functional significance. © 2002 Wiley‐Liss, Inc.
GABA‐B‐related activity in processing of transcallosal response in cat motor cortex
Authors: Chowdhury Syed A. , Matsunami Ken Ichi 
Published: August 2002

AbstractGABA‐ergic characteristics of transcallosal (TC) responses were studied with specific antagonists of both GABA‐A and GABA‐B receptor subtypes. We used a paired‐pulse paradigm to get insight into the role of GABA in interhemispheric interactions between motor cortices. 3‐Amino‐2‐(4‐chlorophenyl)‐propylphosphonic acid (phaclofen) and 3‐aminopropyl‐diethoxymethyl‐phosphinic acid (CGP 35348) were used as GABA‐B antagonists and bicuculline methiodide (BMI) was used to block the GABA‐A receptor. Although both GABA‐A and GABA‐B antagonists increased spike discharge upon transcallosal stimulation, in both pyramidal tract and non‐pyramidal tract neurons, they had different effects on the responses to the first and second stimuli of paired‐pulse stimulation (200 msec interval). Although the inhibition seen with the second stimulus was greatly attenuated by antagonists of the GABA‐B receptor, it was maintained in the presence of the GABA‐A antagonist. These finding support a presynaptic regulation of callosal transmission by GABA‐B receptors in the callosal synapse of the cat motor cortex. © 2002 Wiley‐Liss, Inc.
Extended action of MKC‐242, a selective 5‐HT1A receptor agonist, on light‐induced Per gene expression in the suprachiasmatic nucleus in mice
Authors: Takahashi Satomi , Yoshinobu Yuko , Aida Reiko , Shimomura Haruka , Akiyama Masashi , Moriya Takahiro , Shibata Shigenobu 
Published: August 2002

AbstractWe reported previously that (S)‐5‐[3‐[(1,4‐benzodioxan‐2‐ylmethyl)amino]propoxy]‐1,3‐benzodioxole hydrochloride (MKC‐242) (3 mg kg−1, i.p.), a selective 5‐HT1A receptor agonist, accelerated the re‐entrainment of hamster wheel‐running rhythms to a new 8 hr delayed or advanced light‐dark cycle, and also potentiated the phase advance of the wheel‐running rhythm produced by light pulses. The molecular mechanism underlying MKC‐242‐induced potentiation of this phase shift, however, has not yet been elucidated. We examined the effects of MKC‐242 on light‐induced mPer1 and mPer2 mRNA expression in the suprachiasmatic nucleus (SCN) of mice. MKC‐242 (5 mg kg−1, i.p.) potentiated light‐induced mPer1 and mPer2 expression in the SCN of mice housed in constant darkness for 2 days, when mRNA levels were observed 3 hr after light‐exposure. More potentiating action of MKC‐242 on mPer2 expression in the SCN was observed in mice housed in constant darkness for 9–10 days. This facilitatory action of MKC‐242 on mPer1 expression was antagonized by WAY100635, a selective 5‐HT1A receptor blocker, indicating that MKC‐242 activated 5‐HT1A receptors. Other drugs such as 8‐hydroxy‐dipropylaminotetralin (10 mg kg−1, i.p.), paroxetine (10 mg kg−1, i.p.), buspirone (10 mg kg−1, i.p.), and diazepam (10 mg kg−1, i.p.) did not display a potentiating action on light‐induced mPer1 and mPer2 expression in the SCN. In the behavioral experiments, we found that MKC‐242 (5 mg kg−1, i.p.) potentiated light‐induced phase delays of free‐running rhythm in mice. The present results suggest that prolonged increase of mPer1 or mPer2 expression in the SCN by MKC‐242 may be involved in the potentiation of photic entrainment by MKC‐242 in mice. © 2002 Wiley‐Liss, Inc.
Involvement of the 5‐lipoxygenase pathway in the neurotoxicity of the prion peptide PrP106‐126
Authors: Stewart Leanne R. , White Anthony R. , Jobling Michael F. , Needham B. Elise , Maher Fran , Thyer James , Beyreuther Konrad , Masters Colin L. , Collins Steven J. , Cappai Roberto 
Published: August 2002

AbstractTransmissible spongiform encephalopathies are characterised by the transformation of the normal cellular prion protein (PrPC) into an abnormal isoform (PrPTSE). Previous studies have shown that N‐methyl‐D‐aspartate (NMDA) receptor antagonists can inhibit glutathione depletion and neurotoxicity induced by PrPTSE and a toxic prion protein peptide, PrP106‐126, in vitro. NMDA receptor activation is known to increase intracellular accumulation of Ca2+, resulting in up‐regulation of arachidonic acid (AA) metabolism. This can stimulate the lipoxygenase pathways that may generate a number of potentially neurotoxic metabolites. Because of the putative relationship between AA breakdown and PrP106‐126 neurotoxicity, we investigated AA metabolism in primary cerebellar granule neuron cultures treated with PrP106‐126. Our studies revealed that PrP106‐126 exposure for 30 min significantly up‐regulated AA release from cerebellar granule neurons. PrP106‐126 neurotoxicity was mediated through the 5‐lipoxygenase (5‐LOX) pathway, as shown by abrogation of neuronal death with the 5‐LOX inhibitors quinacrine, nordihydroguaiaretic acid, and caffeic acid. These inhibitors also prevented PrP106‐126‐induced caspase 3 activation and annexin V binding, indicating a central role for the 5‐LOX pathway in PrP106‐126‐mediated proapoptosis. Interestingly, inhibitors of the 12‐lipoxygenase pathway had no effect on PrP106‐126 neurotoxicity or proapoptosis. These studies clearly demonstrate that AA metabolism through the 5‐LOX pathway is an important early event in PrP106‐126 neurotoxicity and consequently may have a critical role in PrPTSE‐mediated cell loss in vivo. If this is so, therapeutic intervention with 5‐LOX inhibitors may prove beneficial in the treatment of prion disorders. J. Neurosci. Res. 65:565–572, 2001. © 2001 Wiley‐Liss, Inc.