Magnetars and pulsars: a missing link

There is growing evidence that soft gamma-ray repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are isolated neutron stars with superstrong magnetic fields, i.e., magnetars, marking them a distinguished species from the conventional species of spindown-powered isolated neutron stars, i.e., radio pulsars. The current arguments in favor of the magnetar interpretation of SGR/AXP phenomenology will be outlined, and the two energy sources in magnetars, i.e. a magnetic dissipation energy and a spindown energy, will be reviewed. I will then discuss a missing link between magnetars and pulsars, i.e., lack of the observational evidence of the spindown-powered behaviors in known magnetars. Some recent theoretical efforts in studying such behaviors will be reviewed along with some predictions testable in the near future.Comment: Invited talk at the Sixth Pacific Rim Conference on Stellar Astrophysics, a tribute to Helmut A. Abt, July 11-17, 2002, Xi'an. To appear in the proceedings (eds. K. S. Cheng, K. C. Leung & T. P. Li

Magnetar-like X-ray Bursts from an Anomalous X-ray Pulsar

Anomalous X-ray Pulsars (AXPs) are a class of rare X-ray pulsars whose energy source has been perplexing for some 20 years. Unlike other, better understood X-ray pulsars, AXPs cannot be powered by rotation or by accretion from a binary companion, hence the designation ``anomalous.'' AXP rotational and radiative properties are strikingly similar to those of another class of exotic objects, the Soft Gamma Repeaters (SGRs). However, the defining property of SGRs, namely their low-energy gamma-ray and X-ray bursts, have heretofore not been seen in AXPs. SGRs are thought to be ``magnetars,'' young neutron stars powered by the decay of an ultra-high magnetic field. The suggestion that AXPs are magnetars has been controversial. Here we report the discovery, from the direction of AXP 1E 1048-5937, of two X-ray bursts that have many properties similar to those of SGR bursts. These events imply a close relationship between AXPs and SGRs, with both being magnetars.Comment: 14 pages, 2 figures, accepted for publication in Nature. Note: The content of this paper is embargoed until 1900 hrs London time / 1400 US Eastern Time on Sept 1

Intestinal transplantation in composite visceral grafts or alone

Under FK 506-based immunosuppression, the entire cadaver small bowel except for a few proximal and distal centimeters was translated to 17 randomly matched patients, of whom two had antigraft cytotoxic antibodies (positive cross-match). Eight patients received the intestine only, eight had intestine in continuity with the liver, and one received a full multivisceral graft that included the liver, stomach, and pancreas. One liver-intestine recipient died after an intestinal anastomotic leak, sepsis, and graft- versus-host disease. The other 16 patients are alive after 1 to 23 months, in one case after chronic rejection, graft removal, and retransplantation. Twelve of the patients have been liberated from total parenteral nutrition, including all whose transplantation was 2 months or longer ago. The grafts have supported good nutrition, and in children, have allowed growth and weight gain. Management of these patients has been difficult and often complicated, but the end result has been satisfactory in most cases, justifying further clinical trials. The convalescence of the eight patients receiving intestine only has been faster and more trouble free than after liver-intestine or multivisceral transplantation, with no greater difficulty in the control of rejection

Intestinal transplantation in composite visceral grafts or alone

Under FK 506-based immunosuppression, the entire cadaver small bowel except for a few proximal and distal centimeters was translated to 17 randomly matched patients, of whom two had antigraft cytotoxic antibodies (positive cross-match). Eight patients received the intestine only, eight had intestine in continuity with the liver, and one received a full multivisceral graft that included the liver, stomach, and pancreas. One liver-intestine recipient died after an intestinal anastomotic leak, sepsis, and graft- versus-host disease. The other 16 patients are alive after 1 to 23 months, in one case after chronic rejection, graft removal, and retransplantation. Twelve of the patients have been liberated from total parenteral nutrition, including all whose transplantation was 2 months or longer ago. The grafts have supported good nutrition, and in children, have allowed growth and weight gain. Management of these patients has been difficult and often complicated, but the end result has been satisfactory in most cases, justifying further clinical trials. The convalescence of the eight patients receiving intestine only has been faster and more trouble free than after liver-intestine or multivisceral transplantation, with no greater difficulty in the control of rejection

Strong and Tunable Nonlinear Optomechanical Coupling in a Low-Loss System

A major goal in optomechanics is to observe and control quantum behavior in a system consisting of a mechanical resonator coupled to an optical cavity. Work towards this goal has focused on increasing the strength of the coupling between the mechanical and optical degrees of freedom; however, the form of this coupling is crucial in determining which phenomena can be observed in such a system. Here we demonstrate that avoided crossings in the spectrum of an optical cavity containing a flexible dielectric membrane allow us to realize several different forms of the optomechanical coupling. These include cavity detunings that are (to lowest order) linear, quadratic, or quartic in the membrane's displacement, and a cavity finesse that is linear in (or independent of) the membrane's displacement. All these couplings are realized in a single device with extremely low optical loss and can be tuned over a wide range in situ; in particular, we find that the quadratic coupling can be increased three orders of magnitude beyond previous devices. As a result of these advances, the device presented here should be capable of demonstrating the quantization of the membrane's mechanical energy.Comment: 12 pages, 4 figures, 1 tabl

Links between traumatic brain injury and ballistic pressure waves originating in the thoracic cavity and extremities

Identifying patients at risk of traumatic brain injury (TBI) is important because research suggests prophylactic treatments to reduce risk of long-term sequelae. Blast pressure waves can cause TBI without penetrating wounds or blunt force trauma. Similarly, bullet impacts distant from the brain can produce pressure waves sufficient to cause mild to moderate TBI. The fluid percussion model of TBI shows that pressure impulses of 15-30 psi cause mild to moderate TBI in laboratory animals. In pigs and dogs, bullet impacts to the thigh produce pressure waves in the brain of 18-45 psi and measurable injury to neurons and neuroglia. Analyses of research in goats and epidemiological data from shooting events involving humans show high correlations (r > 0.9) between rapid incapacitation and pressure wave magnitude in the thoracic cavity. A case study has documented epilepsy resulting from a pressure wave without the bullet directly hitting the brain. Taken together, these results support the hypothesis that bullet impacts distant from the brain produce pressure waves that travel to the brain and can retain sufficient magnitude to induce brain injury. The link to long-term sequelae could be investigated via epidemiological studies of patients who were gunshot in the chest to determine whether they experience elevated rates of epilepsy and other neurological sequelae

Influences on clinical decision-making during a community placement – reflections of a student nurse

The decision-making process in nursing is complex. High quality care is dependent on good clinical judgement and decision-making. Nurses need to be able to justify and defend their clinical decision-making. In this article, the author, a third-year nursing student reflects on an incident from a community placement involving a collaborative, clinical decision. Carper’s (1978) four fundamental patterns of knowing are used to analyse the decision-making process. It is shown that influences on decision-making include prior knowledge and expertise, law and accountability and ethical principles such as respect for autonomy and beneficence. Good communication, interpersonal skills and a person-centred approach have a bearing on decision-making. It is argued that intuitio