Structural ordering of coal char during heat treatment and its impact on reactivity

The effect of heat treatment on the structure of an Australian semi-anthracite char was studied in detail in the 850-1150degreesC temperature range using XRD, HRTEM, and electrical resistivity techniques. It was found that the carbon crystallite size in the char does not change significantly during heat treatment in the temperature range studied, for both the raw coal and its ash-free derivative obtained by acid treatment. However, the fraction of the organized carbon in the raw coal chars, determined by XRD, increased with increase of heat treatment time and temperature, while that for the ash-free coal chars remained almost unchanged. This suggests the occurrence of catalytic ordering during heat treatment, supported by the observation that the electrical resistivity of the raw coal chars decreased with heat treatment, while that of the ash-free coal chars did not vary significantly. Further confirmatory evidence was provided by high resolution transmission electron micrographs depicting well-organized carbon layers surrounding iron particles. It is also found that the fraction of organized carbon does not reach unity, but attains an apparent equilibrium value that increases with increase in temperature, providing an apparent heat of ordering of 71.7 kJ mol(-1) in the temperature range studied. Good temperature-independent correlation was found between the electrical resistivity and the organized carbon fraction, indicating that electrical resistivity is indeed structure sensitive. Good correlation was also found between the electrical resistivity and the reactivity of coal char. All these results strongly suggest that the thermal deactivation is the result of a crystallite-perfecting process, which is effectively catalyzed by the inorganic matter in the coal char. Based on kinetic interpretation of the data it is concluded that the process is diffusion controlled, most likely involving transport of iron in the inter-crystallite nanospaces in the temperature range studied. The activation energy of this transport process is found to be very low, at about 11.8 kJ mol(-1), which is corroborated by model-free correlation of the temporal variation of organized carbon fraction as well as electrical resistivity data using the superposition method, and is suggestive of surface transport of iron. (C) 2002 Elsevier Science Ltd. All rights reserved.

Systemic administration of interleukin-1 beta activates select populations of central amygdala afferents

The central nucleus of the amygdala (CeA) is activated robustly by an immune challenge such as the systemic administration of the proinflammatory cytokine interleukin-1beta (IL-1beta). Because IL-1beta is not believed to cross the blood-brain barrier in any significant amount, it is likely that IL-1beta elicits CeA cell recruitment by means of activation of afferents to the CeA. However, although many studies have investigated the origins of afferent inputs to the CeA, we do not know which of these also respond to IL-1beta. Therefore, to identify candidate neurons responsible for the recruitment of CeA cells by an immune challenge, we iontophoretically deposited a retrograde tracer, cholera toxin b-subunit (CTb), into the CeA of rats 7 days before systemic delivery of IL-1beta (1 mug/kg, i.a.). By using combined immunohistochemistry, we then quantified the number of Fos-positive CTb cells in six major regions known to innervate the CeA. These included the medial prefrontal cortex, paraventricular thalamus (PVT), ventral tegmental area, parabrachial nucleus (PB), nucleus tractus solitarius, and ventrolateral medulla. Our results show that after deposit of CTb into the CeA, the majority of double-labeled cells were located in the PB and the PVT, suggesting that CeA cell activation by systemic IL-1beta is likely to arise predominantly from cell bodies located in these regions. These findings may have significant implications in determining the central pathways involved in generating acute central responses to a systemic immune challenge. J. Comp. Neurol. 452:288-296, 2002. (C) 2002 Wiley-Liss, Inc.

Opposing roles for medial and central amygdala in the initiation of noradrenergic cell responses to a psychological stressor

Psychological stressors trigger the activation of medullary noradrenergic cells, an effect that has been shown to depend upon yet-to-be-identified structures located higher in the brain. To test whether the amygdala is important in this regard, we examined the effects of amygdala lesions on noradrenergic cell responses to restraint, and also looked at whether any amygdala cells that respond to restraint project directly to the medulla. Ibotenic acid lesions of the medial amygdala completely abolished restraint-induced Fos expression in A1 and A2 noradrenergic cells. In contrast, lesions of the central amygdala actually facilitated noradrenergic cell responses to restraint. Tracer deposits in the dorsomedial (but not ventrolateral) medulla retrogradely labelled many cells in the central nucleus of the amygdala, but none of these cells expressed Fos in response to restraint. These data suggest for the first time that the medial amygdala is critical to the activation of medullary noradrenergic cells by a psychological stressor whereas the central nucleus exerts an opposing, inhibitory influence upon noradrenergic cell recruitment. The initiation of noradrenergic cell responses by the medial amygdala does not involve a direct projection to the medulla. Accordingly, a relay through some other structure, such as the hypothalamic paraventricular nucleus, warrants careful consideration.

Reactivity of the isolated perfused rat tail vascular bed

Isolated segments of the perfused rat tail artery display a high basal tone when compared to other isolated arteries such as the mesenteric and are suitable for the assay of vasopressor agents. However, the perfusion of this artery in the entire tail has not yet been used for functional studies. The main purpose of the present study was to identify some aspects of the vascular reactivity of the rat tail vascular bed and validate this method to measure vascular reactivity. The tail severed from the body was perfused with Krebs solution containing different Ca2+ concentrations at different flow rates. Rats were anesthetized with sodium pentobarbital (65 mg/kg) and heparinized (500 U). The tail artery was dissected near the tail insertion, cannulated and perfused with Krebs solution plus 30 µM EDTA at 36oC and 2.5 ml/min and the procedures were started after equilibration of the perfusion pressure. In the first group a dose-response curve to phenylephrine (PE) (0.5, 1, 2 and 5 µg, bolus injection) was obtained at different flow rates (1.5, 2.5 and 3.5 ml/min). The mean perfusion pressure increased with flow as well as PE vasopressor responses. In a second group the flow was changed (1.5, 2, 2.5, 3 and 3.5 ml/min) at different Ca2+ concentrations (0.62, 1.25, 2.5 and 3.75 mM) in the Krebs solution. Increasing Ca2+ concentrations did not alter the flow-pressure relationship. In the third group a similar protocol was performed but the rat tail vascular bed was perfused with Krebs solution containing PE (0.1 µg/ml). There was an enhancement of the effect of PE with increasing external Ca2+ and flow. PE vasopressor responses increased after endothelial damage with air and CHAPS, suggesting an endothelial modulation of the tone of the rat tail vascular bed. These experiments validate the perfusion of the rat tail vascular bed as a method to investigate vascular reactivity.

Effects of ouabain on vascular reactivity

Ouabain is an endogenous substance occurring in the plasma in the nanomolar range, that has been proposed to increase vascular resistance and induce hypertension. This substance acts on the a-subunit of Na+,K+-ATPase inhibiting the Na+-pump activity. In the vascular smooth muscle this effect leads to intracellular Na+ accumulation that reduces the activity of the Na+/Ca2+ exchanger and to an increased vascular tone. It was also suggested that circulating ouabain, even in the nanomolar range, sensitizes the vascular smooth muscle to vasopressor substances. We tested the latter hypothesis by studying the effects of ouabain in the micromolar and nanomolar range on phenylephrine (PE)-evoked pressor responses. The experiments were performed in normotensive and hypertensive rats in vivo, under anesthesia, and in perfused rat tail vascular beds. The results showed that ouabain pretreatment increased the vasopressor responses to PE in vitro and in vivo. This sensitization after ouabain treatment was also observed in hypertensive animals which presented an enhanced vasopressor response to PE in comparison to normotensive animals. It is suggested that ouabain at nanomolar concentrations can sensitize vascular smooth muscle to vasopressor stimuli possibly contributing to increased tone in hypertension.

Determination of reactivity rates of silicate particle-size fractions

The efficiency of sources used for soil acidity correction depends on reactivity rate (RR) and neutralization power (NP), indicated by effective calcium carbonate (ECC). Few studies establish relative efficiency of reactivity (RER) for silicate particle-size fractions, therefore, the RER applied for lime are used. This study aimed to evaluate the reactivity of silicate materials affected by particle size throughout incubation periods in comparison to lime, and to calculate the RER for silicate particle-size fractions. Six correction sources were evaluated: three slags from distinct origins, dolomitic and calcitic lime separated into four particle-size fractions (2, 0.84, 0.30 and <0.30-mm sieves), and wollastonite, as an additional treatment. The treatments were applied to three soils with different texture classes. The dose of neutralizing material (calcium and magnesium oxides) was applied at equal quantities, and the only variation was the particle-size material. After a 90-day incubation period, the RER was calculated for each particle-size fraction, as well as the RR and ECC of each source. The neutralization of soil acidity of the same particle-size fraction for different sources showed distinct solubility and a distinct reaction between silicates and lime. The RER for slag were higher than the limits established by Brazilian legislation, indicating that the method used for limes should not be used for the slags studied here.

Synthesis, characterization and reactivity of new cobalt, palladium and nickel complexes bearing α-diimines and P, O ligands

This work describes the synthesis and characterization of a series of new α-diimine and P,O, β-keto and acetamide phosphines ligands, and their complexation to Ni(II), Co(II),Co(III) and Pd(II) to obtain a series of new compounds aiming to study their structural characteristics and to test their catalytic activity. All the compounds synthesized were characterized by the usual spectroscopic and spectrometric techniques: Elemental Analysis, MALDI-TOF-MS spectrometry, IR, UV-vis, 1H, 13C and 31P NMR spectroscopies. Some of the paramagnetic compounds were also characterized by EPR. For the majority of the compounds it was possible to solve their solid state structure by single crystal X-ray diffraction. Tests for olefin polymerization were performed in order to determine the catalytic activity of the Co(II) complexes. Chapter I presents a brief introduction to homogenous catalysis, highlighting the reactions catalyzed by the type of compounds described in this thesis, namely olefin polymerization and oligomerization and reactions catalyzed by the complexes bearing α-diimines and P,O type ligands. Chapter II is dedicated to the description of the synthesis of new α-diimines cobalt (II) complexes, of general formula [CoX2(α-diimine)], where X = Cl or I and the α-diimines are bis(aryl)acenaphthenequinonediimine) (Ar-BIAN) and 1,4-diaryl-2,3-dimethyl-1,4-diaza-1,3-butadiene (Ar-DAB). Structures solved by single crystal X-ray diffraction were obtained for all the described complexes. For some of the compounds, X-band EPR measurements were performed on polycrystalline samples, showing a high-spin Co(II) (S = 3/2) ion, in a distorted axial environment. EPR single crystal experiments on two of the compounds allowed us to determine the g tensor orientation in the molecular structure. In Chapter III we continue with the synthesis and characterization of more cobalt (II)complexes bearing α-diimines of general formula [CoX2(α-diimine)], with X = Cl or I and α-diimines are bis(aryl)acenaphthenequinonediimine) (Ar-BIAN) and 1,4-diaryl-2,3-dimethyl- 1,4-diaza-1,3-butadiene (Ar-DAB). The structures of three of the new compounds synthesized were determined by single crystal X-ray diffraction. A NMR paramagnetic characterization of all the compounds described is presented. Ethylene polymerization tests were done to determine the catalytic activity of several of the Co(II) complexes described in Chapter II and III and their results are shown. In Chapter IV a new rigid bidentate ligand, bis(1-naphthylimino)acenaphthene, and its complexes with Zn(II) and Pd(II), were synthesized. Both the ligand and its complexes show syn and anti isomers. Structures of the ligand and the anti isomer of the Pd(II) complex were solved by single crystal X-ray diffraction. All the compounds were characterized by elemental analysis, MALDI-TOF-MS spectrometry, and by IR, UV-vis, 1H, 13C, 1H-1H COSY, 1H-13C HSQC, 1H-13C HSQC-TOCSY and 1H-1H NOESY NMR when necessary. DFT studies showed that both conformers of [PdCl2(BIAN)] are isoenergetics and can be obtain experimentally. However, we can predict that the isomerization process is not available in square-planar complex, but is possible for the free ligand. The molecular geometry is very similar in both isomers, and only different orientations for naphthyl groups can be expected. Chapter V describes the synthesis of new P, O type ligands, β-keto phosphine, R2PCH2C(O)Ph, and acetamide phosphine R2PNHC(O)Me, as well as a series of new cobalt(III) complexes namely [(η5-C5H5)CoI2{Ph2PCH2C(O)Ph}], and [(η5- C5H5)CoI2{Ph2PNHC(O)Me}]. Treating these Co(III) compounds with an excess of Et3N, resulted in complexes η2-phosphinoenolate [(η5-C5H5)CoI{Ph2PCH…C(…O)Ph}] and η2- acetamide phosphine [(η5-C5H5)CoI{Ph2PN…C(…O)Me}]. Nickel (II) complexes were also obtained: cis-[Ni(Ph2PN…C(…O)Me)2] and cis-[Ni((i-Pr)2PN…C(…O)Me)2]. Their geometry and isomerism were discussed. Seven structures of the compounds described in this chapter were determined by single crystal X-ray diffraction. The general conclusions of this work can be found in Chapter VI.

Reactivity of bulky tris(Phenylpyrazolyl) methanesulfonate copper(I) complexes towards small unsaturated molecules

Reaction of the tris(3-phenylpyrazolyl)methane sulfonate species (Tpms(Ph))Li with the copper(I) complex [Cu(MeCN)(4)][PF6] affords [Cu(Tpms(Ph))(MeCN)] 1. The latter, upon reaction with equimolar amounts of cyclohexyl-(CyNC) or 2,6-dimethylphenyl (XylNC) isocyanides, or excess CO, furnishes the corresponding Cu(I)complexes [Cu(Tpms(Ph))(CNR)] (R = Cy 2, Xyl 3) or [Cu(Tpms(Ph))(CO)] 4. The ligated isocyanide in 2 or 3 (or the acetonitrile ligand in 1)is displaced by 3-iminoisoindolin-1-one to afford 5, the first copper(I) complex containing an 3-iminoisoindolin-1-one ligand. The ligated acetonitrile in 1 undergoes nucleophilic attack by methylamine to give the amidine complex [Cu(Tpms(Ph)){MeC(NH)NHMe}] 6, whereas only the starting materials were recovered from the attempted corresponding reactions of 2 and 3 with methylamine. Complexes 1 or 6 form the trinuclear hydroxo-copper(II)species [(mu-Cu){Cu(mu-OH) (2)(Tpms(Ph))}(2)] 7 upon air oxidation in moist methanol. In all the complexes the scorpionate ligand facially caps the metal in the N,N,O-coordination mode.

Reactivity of syringyl and guaiacyl lignin units and delignification kinetics in the kraft pulping of eucalyptus globulus wood using Py-Gc-Ms/FID

Eucalyptus globulus sapwood and heartwood showed no differences in lignin content (23.0% vs. 23.7%) and composition: syringyl-lignin (17.9% vs. 18.0%) and guaiacyl-lignin (4.8% vs. 5.2%). Delignification kinetics of S- and G-units in heartwood and sapwood was investigated by Py-GC–MS/FID at 130, 150 and 170 °C and modeled as double first-order reactions. Reactivity differences between S and G-units were small during the main pulping phase and the higher reactivity of S over G units was better expressed in the later pulping stage. The residual lignin composition in pulps was different from wood or from samples in the initial delignification stages, with more G and H-units. S/G ratio ranged from 3 to 4.5 when pulp residual lignin was higher than 10%, decreasing rapidly to less than 1. The S/H was initially around 20 (until 15% residual lignin), decreasing to 4 when residual lignin was about 3%.

Reactivity of human fetal and adult immortalized hepatocytes to potentially toxic bilirubin and bile acid species

Dissertação apresentada para a obtenção do Grau de Mestre em Genética Molecular e Biomedicina, pela Universidade Nova de Lisboa, Faculdade de Ciências e Tecnologia

Amygdala activation in response to 2D and 3D emotion-inducing stimuli

Studying changes in brain activation according to the valence of emotion-inducing stimuli is essential in the research on emotions. Due to the ecological potential of virtual reality, it is also important to examine whether brain activation in response to emotional stimuli can be modulated by the three-dimensional (3D) properties of the images. This study uses functional Magnetic Resonance Imaging to compare differences between 3D and standard (2D) visual stimuli in the activation of emotion-related brain areas. The stimuli were organized in three virtual-reality scenarios, each with a different emotional valence (pleasant, unpleasant and neutral). The scenarios were presented in a pseudo-randomized order in the two visualization modes to twelve healthy males. Data were analyzed through a GLM-based fixed effects procedure. Unpleasant and neutral stimuli activated the right amygdala more strongly when presented in 3D than in 2D. These results suggest that 3D stimuli, when used as “building blocks” for virtual environments, can induce increased emotional loading, as shown here through neuroimaging.

Cross-reactivity of antibodies in human infections by the kinetoplastid protozoa Trypanosoma cruzi, Leishmania chagasi and Leishmania (Viannia) braziliensis

We have detected antibodies, in the sera of Chagas disease, Kala-azar and Mucocutaneous leishmaniasis patients, that bind multiple antigens shared between the three causative agents. The Chagas disease sera showed 98 to 100% positive results by ELISA when the Leishmania braziliensis and Leishmania chagasi antigens were used, respectively. The Kala-azar sera showed 100% positive results with Trypanosoma cruzi or L. braziliensis antigens by immunofluorescence assays. The antibodies in the sera of Mucocutaneous leishmaniasis patients showed 100% positive results by ELISA assays with T. cruzi or L. chagasi antigens. Furthermore, the direct agglutination of L. chagasi promastigotes showed that 95% of Kala-azar and 35% of Mucocutaneous leishmaniasis sera agglutinated the parasite in dilutions above 1:512. In contrast, 15% of Chagas sera agglutinated the parasite in dilutions 1:16 and below. Western blot analysis showed that the Chagas sera that formed at least 24 bands with the T. cruzi also formed 13 bands with the L. chagasi and 17 bands with the L. braziliensis. The Kala-azar sera that recognized at least 29 bands with the homologous antigen also formed 14 bands with the T. cruzi and 10 bands with the L. braziliensis antigens. Finally, the Mucocutaneous leishmaniasis sera that formed at least 17 bands with the homologous antigen also formed 10 bands with the T. cruzi and four bands with the L. chagasi antigens. These results indicate the presence of common antigenic determinants in several protozoal proteins and, therefore, explain the serologic cross-reactions reported here.

Histoplasmin and paracoccidioidin skin reactivity in infantile population of Northern Argentina

In order to estimate ages at which etiological agents of systemic mycoses initiate infection, histoplasmin and paracoccidioidin skin tests were performed in 344 children of both sexes, between 2 and 15 years old. They were selected from a statistically significant population sample Gral. San Martín city (Northeast Argentina). Tests were read 48h after injection and considered positive if a 5 mm on larger induration was present. Circulating antibodies were also evaluated by agar gel immunodiffusion. The overall infection rate for H. capsulatum was 9.2%, belonging to children from 4 to 14 years old, without significant differences among sexes. Five children from 2 to 14 years old were positive to paracoccidioidin (1.6%). None of the children had specific antibodies neither signs of active mycosis. Results show H. capsulatum infection can be found from age 4, while for P. brasiliensis the lower limit was two years old. These findings may contribute to better knowledge on infantile fungal infection in a geographical region where no previous references can be found.

REACTIVITY OF ANTI-GP43 ANTIBODIES FROM PARACOCCIDIOIDES BRASILIENSIS ANTISERUM WITH EXTRACTS FROM CUTANEOUS LESIONS OF LOBO'S DISEASE: PRELIMINARY NOTE

We demonstrated through several immunochemical tests the presence of GP-43 from P. brasiliensis in extracts of cutaneous lesions from Jorge Lobo's disease. This glicoprotein is one of the immunodominant antigens in this species, and is used to identify it. The demonstration of GP-43 tissues infected by the agent of Jorge Lobo's disease is an additional evidence for classifying it in the genera Paracoccidioides, species loboi

Dermatophytosis: association between ABO blood groups and reactivity to the trichophytin

The authors investigated the relationship between dermatophytosis and ABO blood groups through blood typing, identification of isolated dermatophytes and specific cellular immune response of 40 individuals carriers of this mycosis. They verified that the fungus Trichophyton rubrum, isolated from 54.5% of the patients, was more frequent in individuals belonging to blood group A. The cellular immune response, evaluated through the trichophytin antigen, was positive in 25% of the studied patients; the presence of immediate reactions (30 minutes) was verified in 35%. The blood group distribution among patients with dermatophytosis and control groups was, respectively: 47.5% X 36% in group A, 40% X 50% in group O, 12.5% X 11% in group B. Even though the authors have found a higher number of patients belonging to blood group A infected by T. rubrum, these results suggest that there is no statistical evidence that these individuals are more susceptible to dermatophytosis.