RESUMO
The gas activity of comet C/1999 S4 (LINEAR) was monitored at radio wavelengths during its disruption. A runaway fragmentation of the nucleus may have begun around 18 July 2000 and proceeded until 23 July. The mass in small icy debris (=30-centimeter radius) was comparable to the mass in the large fragments seen in optical images. The mass budget after breakup suggests a small nucleus ( approximately 100- to 300-meter radius) that had been losing debris for weeks. The HNC, H2CO, H2S, and CS abundances relative to H2O measured during breakup are consistent with those obtained in other comets. However, a deficiency in CH3OH and CO is observed.
RESUMO
Spectra obtained from ground-based radio telescopes show the progressive release of CO, CH3OH, HCN, H2O (from OH), H2S, CS, H2CO, CH3CN, and HNC as comet Hale-Bopp (C/1995 01) approached the sun from 6.9 to 1.4 astronomical units (AU). The more volatile species were relatively more abundant in the coma far from the sun, but there was no direct correlation between overabundance and volatility. Evidence for H2O sublimation from icy grains was seen beyond 3.5 AU from the sun. The change from a CO-driven coma to an H2O-driven coma occurred at about 3 AU. The gas outflow velocity and temperature increased as Hale-Bopp approached the sun.
Assuntos
Meteoroides , Carbono/análise , Monóxido de Carbono/análise , Poeira Cósmica , Gases , Hidrogênio/análise , Gelo , Metanol/análise , Nitrogênio/análise , Análise Espectral , Temperatura , ÁguaRESUMO
Ciao is a website specifically designed for young people and focuses mainly on health issues. This report presents the process of setting up the site and a first evaluation undertaken by using two self-administered questionnaires administered via the website itself. It suggests that it is possible to provide young people with authoritative health information and to facilitate their access to counseling and health care facilities by having young people use such a website.
Assuntos
Serviços de Saúde do Adolescente/normas , Educação em Saúde/métodos , Promoção da Saúde/métodos , Serviços de Informação/normas , Internet/normas , Adolescente , Serviços de Saúde do Adolescente/estatística & dados numéricos , Feminino , Educação em Saúde/normas , Promoção da Saúde/normas , Humanos , Serviços de Informação/estatística & dados numéricos , Internet/estatística & dados numéricos , Masculino , Inquéritos e Questionários , SuíçaRESUMO
This communication describes a patient with Down's syndrome, in whom an Ebstein's anomaly of the tricuspid valve was found at autopsy. The association of these two conditions appears to be rare.
Assuntos
Síndrome de Down/complicações , Anomalia de Ebstein/complicações , Adolescente , Anomalia de Ebstein/patologia , Feminino , HumanosRESUMO
Capacitation is characterized by a hyperactivated pattern of sperm motility. The acquisition of highly motility is present in the early stages of capacitation. Sperm progressive motility is one of the most important parameters for determining the suitability of semen for processing. However, previous studies have shown that some sperm showing good motility have membrane damage. The aim of our study was to characterize the lectin staining pattern on the sperm plasma membrane of unselected and selected human sperm of normozoospermic donors. Sperm selection was performed by the swim-up technique. Fourteen samples from healthy consenting donors classified as normozoospermic according to the World Health Organization were used. We observed changes in the distribution of the carbohydrate residues after the swim-up selection. With Triticum vulgaris, the most abundant pattern was dotted labeling all over the head plasma membrane in the unselected sperm. However, this lectin was distributed homogenously over the acrosomal region after selection. With Arachis hypogaea, the most abundant pattern in fresh sperm was a highly stained acrosomal region. In the highly motility sperm population, the most frequent pattern was dotted fluorescence on the acrosomal region and a highly stained equatorial segment. Meanwhile, with the Aleuria aurantia and Canavalia ensiformis lectins, the most representative patterns were the same before and after the swim-up selection. Our data indicate that modifications which occur in carbohydrate residues during swim-up selection could be important for the regulation of progressive motility and prepare the sperm for capacitation.
Assuntos
Lectinas/metabolismo , Espermatozoides/metabolismo , Acrossomo/metabolismo , Sítios de Ligação , Membrana Celular/metabolismo , Separação Celular/métodos , Concanavalina A/metabolismo , Humanos , Masculino , Aglutinina de Amendoim/metabolismo , Receptores Mitogênicos/metabolismo , Capacitação Espermática/fisiologia , Motilidade dos Espermatozoides/fisiologia , Espermatozoides/fisiologia , Coloração e Rotulagem , Aglutininas do Germe de Trigo/metabolismoRESUMO
On 4 July 2005, many observatories around the world and in space observed the collision of Deep Impact with comet 9P/Tempel 1 or its aftermath. This was an unprecedented coordinated observational campaign. These data show that (i) there was new material after impact that was compositionally different from that seen before impact; (ii) the ratio of dust mass to gas mass in the ejecta was much larger than before impact; (iii) the new activity did not last more than a few days, and by 9 July the comet's behavior was indistinguishable from its pre-impact behavior; and (iv) there were interesting transient phenomena that may be correlated with cratering physics.
Assuntos
Meteoroides , Poeira Cósmica , Júpiter , Compostos Orgânicos , FotometriaRESUMO
When comet C/1995 O1 (Hale-Boop) was discovered, at a distance of seven astronomical units from the sun, it was more than one hundred times brighter than comet Halley at the same distance. A comet's brightness is derived from the reflection of sunlight from dust grains driven away from the nucleus by the sublimation of volatile ices. Near the sun, sublimation of water ice (a main constituent of comet nuclei) is the source of cometary activity; but at its current heliocentric distance, Hale-Boop is too cold for this process to operate. Other comets have shown activity at large distances, and in the case of comet Schwassmann-Wachmann 1, carbon monoxide has been detected in quantities sufficient to generate its observed coma. Here we report the detection of CO emission from Hale-Boop, at levels indicating a very large rate of outgassing. Several other volatile species were searched for, but not detected. Sublimation of CO therefore appears to be responsible for the present activity of this comet, and we anticipate that future observations will reveal the onset of sublimation of other volatile species as the comet continues its present journey towards the sun.
Assuntos
Monóxido de Carbono/análise , Meteoroides , Meio Ambiente Extraterreno , Formaldeído/análise , Cianeto de Hidrogênio/análise , Metanol/análise , Análise EspectralRESUMO
In July 1994, the collisions of the fragments of comet Shoemaker-Levy 9 with Jupiter resulted in dramatic changes in the planet's atmosphere. Observations of the events suggest that the composition and thermal properties of the atmosphere were considerably modified at the impact sites, with the changes persisting for times lasting from minutes to weeks (see, for example, refs 1-4). Here we report observations of the impact sites at millimetre wave-lengths, which reveal strong emission lines associated with carbon monoxide, carbonyl sulphide and carbon monosulphide. The abundance of carbon monoxide in the jovian atmosphere is normally very low; carbonyl sulphide and carbon monosulphide, on the other hand, have not hitherto been detected. We find that the largest fragments (G and K) each produced approximately 10(14) g of carbon monoxide, 3 x 10(12) g of carbonyl sulphide and 3 x 10(11) g of carbon monosulphide, most probably by shock-induced chemical reactions. Our observations also place firm constraints on the thermal response of Jupiter's stratosphere to the impacts.