RESUMEN

The nature of dark matter remains mysterious, with luminous material accounting for at most approximately 25 per cent of the baryons in the Universe. We accordingly undertook a survey looking for the microlensing of stars in the Large Magellanic Cloud (LMC) to determine the fraction of Galactic dark matter contained in massive compact halo objects (MACHOs). The presence of the dark matter would be revealed by gravitational lensing of the light from an LMC star as the foreground dark matter moves across the line of sight. The duration of the lensing event is the key observable parameter, but gives non-unique solutions when attempting to estimate the mass, distance and transverse velocity of the lens. The survey results to date indicate that between 8 and 50 per cent of the baryonic mass of the Galactic halo is in the form of MACHOs (ref. 3), but removing the degeneracy by identifying a lensing object would tighten the constraints on the mass in MACHOs. Here we report a direct image of a microlens, revealing it to be a nearby low-mass star in the disk of the Milky Way. This is consistent with the expected frequency of nearby stars acting as lenses, and demonstrates a direct determination of a lens mass from a microlensing event. Complete solutions such as this for halo microlensing events will probe directly the nature of the MACHOs.

RESUMEN

This article proposes an experimental field protocol for investigating the postmortem interval using specially designed apparatus and human and pig cadavers. We further propose that this goal can only be achieved by a multidisciplinary group, comprised of forensic entomologists, pathologists, and anthropologists. The apparatus and collecting methods described by the authors establish the means by which data can be collected on several fronts simultaneously: the sequential arrival and variety of insects in the decay process, the character and manner of soft tissue decomposition, the sequence and nature of bone exposure and order of disarticulation of skeletal remains, and the influence of climate and season on decay rates and arthropod succession. A central feature of this protocol involves the construction and use of a dual-functioning insect trap that allows separate but simultaneous capture of arriving and emerging populations while successional and decompositional processes of the cadaver are left intact. Results of trap performance tests in an arid climate and preliminary arthropod data collected from field-exposed pig carcasses are presented. The use of this protocol could provide important and badly needed baseline data for both medical investigators and law enforcement personnel, information that is critical to understanding the causes, manner, and time of death, which the law requires to be ascertained.

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RESUMEN

Drowning as a form of subtle fatal child abuse is difficult to distinguish from accidental immersion or from sudden unexpected natural death when the circumstances of immersion are concealed. Homicidal drownings are unwitnessed, usually occurring in the home, and the victims are young, either infants or toddlers. Accidental drownings are more likely to involve toddlers or older children in public areas such as swimming pools, drainage ditches, lakes, and rivers. This is especially true in rural areas. In cities, bathtubs remain a major site of accidental childhood drownings. Perpetrators of deliberate drownings often fit the sociopathologic profile of a child abuser. Because there is often a survival interval between immersion and death, pathologic findings consistent with postimmersion syndrome suggest the cause of death. Foreign material in the lungs, if immersion was other than in clear tap water, and injuries of the face are other positive correlating factors. A thorough investigation of the circumstances and cooperation between the investigating agency and the pathologist are essential to determine the correct manner of death in these cases.

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