X-ray insights into star and planet formation.

Although stars and planets form in cold environments, X-rays are produced in abundance by young stars. This review examines the implications of stellar X-rays for star and planet formation studies, highlighting the contributions of NASA's (National Aeronautics and Space Administration) Chandra X-ray Observatory. Seven topics are covered: X-rays from protostellar outflow shocks, X-rays from the youngest protostars, the stellar initial mass function, the structure of young stellar clusters, the fate of massive stellar winds, X-ray irradiation of protoplanetary disks, and X-ray flare effects on ancient meteorites.

A reappraisal of the habitability of planets around M dwarf stars.

Stable, hydrogen-burning, M dwarf stars make up about 75% of all stars in the Galaxy. They are extremely long-lived, and because they are much smaller in mass than the Sun (between 0.5 and 0.

Discovery of X-rays from the protostellar outflow object HH2.

Herbig-Haro (HH) objects have been known for 50 years to be luminous condensations of gas in star-forming regions, but their underlying physical nature is still being elucidated. Previously suggested models encompass newborn stars, stellar winds clashing with nebular material, dense pockets of interstellar gas excited by shocks from outflows, and interstellar 'bullets' (ref. 6).

Rapid X-ray flaring from the direction of the supermassive black hole at the Galactic Centre.

The nuclei of most galaxies are now believed to harbour supermassive black holes. The motions of stars in the central few light years of our Milky Way Galaxy indicate the presence of a dark object with a mass of about 2.6 x 106 solar masses (refs 2, 3).

Hot plasma and black hole binaries in starburst galaxy M82.

High-resolution x-ray observations of the prototype starburst galaxy Messier 82 (M82) obtained with the advanced CCD (charge-coupled device) imaging spectrometer on board the Chandra X-ray Observatory provide a detailed view of hot plasma and energetic processes. Plasma with temperature of about 40,000,000 kelvin fills the inner 1 kiloparsec, which is much hotter than the 1,000,000 to 2,000,000 kelvin interstellar medium component in the Milky Way Galaxy. Produced by many supernova explosions, this central region is overpressurized and drives M82's prominent galactic wind into the intergalactic medium.

A new mechanism for the formation of meteoritic kerogen-like material.

The carbon in ancient carbonaceous chondritic meteorites is mainly in a hydrocarbon composite similar to terrestrial kerogen, a cross-linked structure of aliphatic and aromatic hydrocarbons. Until recently, the composite has been commonly thought to have been produced in the early solar nebula by a Fischer-Tropsch-type process, involving the catalytic synthesis of hydrocarbons from carbon monoxide and hydrogen on grain surfaces. Instead, the aromatic hydrocarbons may form in gas-phase pyrolysis of simple aliphatics like acetylene and methane by a mechanism developed recently to explain formation of soot in combustion and of aromatic molecules in circumstellar envelopes.

Pathological identification in twins.

In summary, in addition to the cultural, parental, developmental, and dynamic factors which support mutual identification and/or failure of separation between twins, it is my thesis that the basic early identifications between twins rely heavily on relatively conflict-free perceptual modes (visual, auditory, kinesthetic, etc.) quite different from the conflict-laden drive modes we usually think of when considering identification. Furthermore, identification based on perceptual modes, which are relatively free of conflict in early development, become extremely difficult to analyze, as analytic progress depends on conflict.

The decision to hospitalize.

The authors explored determinants of psychiatric hospitalization in four Manhattan general hospital emergency rooms and found that although the nature and severity of a patient's problem played the most important role in the decision to hospitalize, the facility involved was also a determining factor. The findings are discussed in relation to policy concerning staffing and organization of emergency room services and future studies of service delivery in this area.

Continuing education, recertification, and examination anxiety.

A substantial majority of the 645 psychiatrists responding to a questionnaire survey favored mandatory continuing education and evidence of continuing education as a requirement for relicensure. The respondents' overwhelming repudiation of recertification may be based on examination anxiety. The respondents recognized the value of continuing education, were even willing to document it in order to be relicensed, but did not wish to examined.