On the Production and Kinematics of Sodium Atoms in the Head of Comet Hale-Bopp

in Bulletin of the American Astronomical Society (1997, July 01), 29

The interpretation of the presence and extent of the atomic sodium observed in comet Hale-Bopp raises a number of questions related to the production, motion, and lifetime of these Na atoms under the ... [more ▼]

The interpretation of the presence and extent of the atomic sodium observed in comet Hale-Bopp raises a number of questions related to the production, motion, and lifetime of these Na atoms under the action of the solar radiation near 1 AU. Here we report on data which pertain to the study of sodium in the head of the comet, yielding information on the Na emission in the coma out to ~ 0.15 x 10(6) km on the sunward side, to ~ 0.2 x 10(6) km tailwards. The observations were carried out at the Observatoire de Haute-Provence, with the 1.93 m telescope and the ELODIE spectrometer, which is fed by a pair of optical fibers with 2-arcsec apertures separated by 1.8 arcmin. In particular, spectra were obtained on 15-17 April, 1997, near the discovery date of the sodium tail at the La Palma Observatory. These spectra (resolution ~ 7 km/s) were used to determine Na D line profiles, as well as the relative intensities of the emissions corresponding to the two positions observed simultaneously. The main outcome of our first analysis concerns the profiles recorded some distance away from the optical centre, which all show velocity shifts and asymmetric line broadening in the direction of anti-sunward velocities. Some evidence is found to suggest the existence of an extended or multi-source production of sodium atoms, at least in the coma. Another series of spectra secured just before perihelion, 25-27 March, was analysed in the same way as the April spectra. Comparison between the two sets of data provides a nice illustration of the marked influence of the heliocentric radial velocity, not only upon the strength of the fluorescence ("Swings effect"), but also upon the motion of the emitting atoms, which are accelerated by the radiation pressure to widely different degrees as their excitation wavelengths fall at different places within the Fraunhofer Na D line profiles. [less ▲]

Stratégies et médias pédagogiques pour l'apprentissage et l'évaluation dans l'enseignement Supérieur : Actes du 15° colloque de l'Association Internationale de Pédagogie Universitaire

Book published by ULg (1997)

Distance learning and education for diabetes care

in Journal of the Diabetic Association of India (1997, July), 37(3), 71-76

Comparison of the binding constant values of complexes of different antimycotic imidazole derivatives with cyclodextrin obtained by capillary electrophoresis and phase solubility diagram

Poster (1997, July)

Study of the combined effects of cyclodextrins and buffer type on the solubility of miconazole

Poster (1997, July)

Vasotocinergic Innervation of Areas Containing Aromatase-Immunoreactive Cells in the Quail Forebrain

in Journal of Neurobiology (1997), 33(1), 45-60

In the male quail forebrain, aromatase-immunoreactive (ARO-ir) elements are clustered within the sexually dimorphic medial preoptic nucleus (POM), nucleus striae terminalis (nST), nucleus accumbens (nAc ... [more ▼]

In the male quail forebrain, aromatase-immunoreactive (ARO-ir) elements are clustered within the sexually dimorphic medial preoptic nucleus (POM), nucleus striae terminalis (nST), nucleus accumbens (nAc), and ventromedial and tuberal hypothalamus. These ARO-ir cells are sensitive to testosterone and its metabolites: Their number and size increase after exposure to these steroids. The POM and lateral septum are also characterized by a dense vasotocinergic innervation that is also sensitive to testosterone. We analyzed here the anatomical relationships between ARO-ir elements and VT-ir fibers in the quail prosencephalon. Sequential staining for vasotocin, aromatase, or vasotocin plus aromatase was performed on adjacent 30-microm-thick cryostat sections. High concentrations of thin VT-ir fibers were observed within the POM, nST, lateral septum, periventricular mesencephalic central gray, and ventromedial and tuberal hypothalamus. There was a close correspondence between the extension of the ARO-ir cells and of VT-ir fibers. In double-labeled sections, all clusters of ARO-ir cells with the exception of those located in the nAc were embedded in a dense network of VT-ir fibers. Many of the VT-ir terminals appeared to end in the neuropile surrounding ARO-ir elements rather than directly on their cell bodies. This study supports the idea that the testosterone-dependent aromatase system is directly innervated by a testosterone-dependent peptidergic system. Aromatase-containing cells could therefore be modulated by steroids both directly and indirectly through the vasotocin system. Alternatively, this neuroanatomical arrangement may mediate the control of vasotocin synthesis or release by steroids. Functional studies demonstrate that both aromatase and vasotocin affect reproductive behavior in quail, and the present data provide anatomical support for the integration of these effects. [less ▲]

Chronic varicella-zoster virus skin lesions in patients with human immunodeficiency virus are related to decreased expression of gE and gB

in Journal of Infectious Diseases (1997), 176(1), 261-264

The pathogenesis of chronic, verrucous varicella-zoster virus (VZV) cutaneous lesions in human immunodeficiency virus (HIV)-infected persons is unknown. It has been hypothesized that these lesions are due ... [more ▼]

The pathogenesis of chronic, verrucous varicella-zoster virus (VZV) cutaneous lesions in human immunodeficiency virus (HIV)-infected persons is unknown. It has been hypothesized that these lesions are due to an altered pattern of virus gene expression. Immediate early and late (L) gene expression in five chronic verrucous VZV lesions, four full-blown herpes zoster vesicular lesions in HIV-infected persons, and eight vesicular herpes zoster lesions in immunocompetent individuals was semiquantitatively assessed immunohistochemically using specific antibodies to the IE63, gE (L), and gB (L) proteins. All patients had evidence of IE63 expression in keratinocytes; however, gE expression was either weak or absent in keratinocytes of three verrucous lesions, and gB was either weak or absent in two. These results suggest that chronic VZV skin lesions are associated with diminished gE and gB expression. It is inferred that the VZV behavior in keratinocytes may vary from a latency-like state to a fully developed, productive infection. [less ▲]

Art, Mail-art, “Médiart”

in Cyber-Flux-News (1997)

Dual Multimodular Class a Penicillin-Binding Proteins in Mycobacterium Leprae

in Journal of Bacteriology (1997), 179(14), 4627-4630

The ponA gene of cosmid L222 of the Mycobacterium leprae genome library encodes a multimodular class A penicillin-binding protein (PBP), PBP1. The PBP, labelled with a polyhistidine sequence, has been ... [more ▼]

The ponA gene of cosmid L222 of the Mycobacterium leprae genome library encodes a multimodular class A penicillin-binding protein (PBP), PBP1. The PBP, labelled with a polyhistidine sequence, has been produced in Escherichia coli, extracted from the membranes with 3-[(3-cholamidopropyl)-dimethylammonio]-1-propane-sulfonate (CHAPS) and purified by Ni2(+)-nitrilotriacetic acid-agarose chromatography. In contrast to the pon1-encoded class A PBP1, PBP1 undergoes denaturation at temperatures higher than 25 degrees C, it catalyzes acyl transfer reactions on properly structured thiolesters, and it binds penicillin with high affinity. [less ▲]

Apports et perspectives des dérivés de l'hémoglobine

in Schweizerische Medizinische Wochenschrift (1997), 127(25), 1088-96

Anoxia-reoxygenation leads to severe metabolic alterations, which result in a generalized inflammatory reaction and multiple organ dysfunction. Direct blood transfusion limits these alterations, but is ... [more ▼]

Anoxia-reoxygenation leads to severe metabolic alterations, which result in a generalized inflammatory reaction and multiple organ dysfunction. Direct blood transfusion limits these alterations, but is accompanied by risk of transmission of infections or viral diseases. To avoid these risks, "blood substitutes" have been designed. The modified hemoglobins are not true blood substitutes because they do not possess the complex functions of erythrocytes. They are only oxygen carriers, with a short intravascular life, adapted for temporary use. They are stable, devoid of toxicity and antigenicity, and are able to carry and deliver O2 without regulation of this oxygen transport and without chemical reaction with O2. They possess rheologic properties and an oncotic pressure like those of blood. The use of natural hemoglobin solutions, obtained after lysis of erythrocytes, remains "at risk" because these solutions easily form methemoglobin, increase the oncotic pressure, present renal toxicity, and possess a too high affinity for O2. For these reasons, 5 types of modified hemoglobin solutions have been designed, prepared from human or bovine hemoglobin or by genetic engineering. These hemoglobins are highly purified to eliminate trace amounts of stroma, lipids and endotoxins, which are responsible for acute toxicity. They are modified by internal cross-linking between the monomers, or by binding to macromolecules. Afterwards, they can be polymerized or encapsulated in liposomes. The purpose of these modifications is to modulate the affinity for O2 (by decreasing the binding of O2 and increasing its delivery to tissue), to reduce the dissociation into monomers and to guard against oxidation into methemoglobin. Encapsulation in liposomes allows co-encapsulation of effector molecules and protective substances. Genetic engineering allows the production of recombinant hemoglobin with selective modifications. The modified hemoglobin solutions are essentially used in hemorrhagic shock and perioperative hemodilution. Experimental work in animals has afforded good results: restoration of normal O2 pressure and no toxicity. These assays allow frequent observation of an unexpected rapid hypertensive effect, transient, reversible, and that could be controlled by antihypertensive drugs. The mechanisms of this hypertensive effect remain controverted (stimulation of endothelin production, inhibition of nitric oxide effects, etc.). In humans, studies with healthy volunteers have been completed, while phase II clinical studies are under way in hypovolemic shock, in major abdominal, orthopedic and cardiac surgery, in stroke and in intensive care patients after surgery. The detailed results are awaited, but the modified hemoglobin solutions already appear to be without toxicity and present the same hypertensive effect as observed in animals. However, until now only low doses have been used, and the catabolism of these solutions remains largely unknown. [less ▲]