Gravitomagnetism and the Clock Effect

The main theoretical aspects of gravitomagnetism are reviewed. It is shown that the gravitomagnetic precession of a gyroscope is intimately connected with the special temporal structure around a rotating mass that is revealed by the gravitomagnetic clock effect. This remarkable effect, which involves the difference in the proper periods of a standard clock in prograde and retrograde circular geodesic orbits around a rotating mass, is discussed in detail. The implications of this effect for the notion of ``inertial dragging'' in the general theory of relativity are presented. The theory of the clock effect is developed within the PPN framework and the possibility of measuring it via spaceborne clocks is examined.Comment: 27 pages, LaTeX, submitted to Proc. Bad Honnef Meeting on: GYROS, CLOCKS, AND INTERFEROMETERS: TESTING GENERAL RELATIVITY IN SPACE (22 - 27 August 1999; Bad Honnef, Germany

An alternative electric-field spectrum for laser-driven atomic systems

We adopt an open systems perspective to calculate the power spectrum associated with the electric field generated by an atomic dipole moment undergoing resonant laser-driving. This spectrum has a similar triplet shape to the Mollow spectrum and contains a similar amount of information. This is surprising, since the Mollow triplet derives from the Glauber two-time correlation function, which represents the average energy-intensity of a superposition of waves taken at different times. In contrast, our spectrum derives from a correlation function defined in terms of single-time expectation values of the electric source-field. Although they are derived from very different correlation functions, both spectra reflect the quantum-mechanical level-structure of the atomic source

Sensation Seeking and Risk-Taking Propensity as Mediators in the Relationship between Childhood Abuse and HIV-Related Risk Behavior

Objectives Although a wealth of literature suggests that childhood physical, emotional, and sexual abuse are related to later-life HIV-related risk behaviors, few studies have explored disinhibition (e.g., impulsivity, risk-taking propensity, and sensation-seeking) as a risk factor in this relationship. Method This cross-sectional study examined impulsivity, risk-taking propensity, and sensation seeking as mediators in the relationship between abuse history and engagement in HIV-related risk behaviors among a sample of 96 inner-city African American adolescents. Results Findings indicated that abuse history was positively related to self-reported engagement in HIV-related risk behaviors (B = 0.027, SE 0.008, β = .32, sr2 = .105, p = .001), as well as risk-taking propensity (B = 0.35,SE 0.11, β = .30, sr2 = .090, p = .003) and sensation seeking (B = 0.17, SE 0.05, β = .35, sr2 = .124, p = .0004). Abuse history was not related to impulsivity. Further, while sensation-seeking and risk-taking propensity (to a lesser extent) mediated this relationship, impulsivity did not. Conclusions These findings provide an initial step in the examination of the mechanisms underlying the relationship between childhood abuse and engagement in HIV-related risk behaviors

Determinação do nível de gravidade do trauma Determination of trauma severity level by means of the injury severity score

Trata-se de estudo prospectivo que teve por objetivo caracterizar a gravidade do trauma de pacientes hospitalizados, através do "Injury Severity Score" (ISS). Foram analisados 100 pacientes de trauma internados em uma instituição referência para trauma localizada em São Paulo, Brasil. Do total de pacientes, 68 sofreram trauma fechado e 32 trauma penetrante. Dentre os pacientes de trauma fechado, 53,0% sofreram trauma leve (ISS 1-15), 29,4% trauma moderado (ISS 16-24) e 17,6% trauma grave (ISS > 25) enquanto que 34,4% dos pacientes de trauma penetrante sofreram trauma leve, 18,7% trauma moderado e 46,9% trauma grave. A média e desvio-padrão dos ISSs dos pacientes de trauma fechado e penetrante foi, respectivamente, de 14,9 &plusmn; 8,1 e 20,8 &plusmn; 11,0, correspondendo a um percentual de mortos de 11,8% e 12,5%.<br>The severity of traumas in hospitalized patients was characterized by means of the Injury Severity Score (ISS) was studied prospectively. One hundred trauma patients hospitalized in a trauma referral health facility located in S. Paulo, Brazil, were analyzed. Of the total number of patients, 68 had blunt trauma and 32 penetrating trauma. As to ISS, it was discovered that 53.0% of the blunt trauma patients had mild trauma (ISS 1-15), 29,4% moderate trauma (ISS 16-24), and 17.6% showed severe trauma (ISS 25); 34.4% of the penetrating trauma patients had mild trauma, 18.7% moderate trauma and 46.9% severe trauma. The mean and standard deviations relationg to the ISS of blut and penetrating trauma patients were, respectively, 14.9 &plusmn; 8.1 and 20.8 &plusmn; 11.0; the respective mortality rates were of 11.8% and 12.5