Nonlinear femtosecond pulse compression at high average power levels by use of a large-mode-area holey fiber.

We demonstrate that nonlinear fiber compression is possible at unprecedented average power levels by use of a large-mode-area holey (microstructured) fiber and a passively mode-locked thin disk Yb:YAG laser operating at 1030 nm. We broaden the optical spectrum of the 810-fs pump pulses by nonlinear propagation in the fiber and remove the resultant chirp with a dispersive prism pair to achieve 18 W of average power in 33-fs pulses with a peak power of 12 MW and a repetition rate of 34 MHz. The output beam is nearly diffraction limited and is linearly polarized.

Comparative study of large-mode holey and conventional fibers.

Little information exists regarding how large-mode holey fibers compare, in practical terms, with their conventional counterparts. We present what is to our knowledge the first experimental study of mode area and bend loss for a range of large-mode holey and conventional fibers. It is demonstrated here that large-mode holey fibers exhibit mode areas and bending losses that are comparable to those of conventional fibers at 1.55mu . However, the novel wavelength dependence of the numerical aperture in a holey fiber offers a significant advantage for broadband and short-wavelength applications in which single-mode operation is required.

Long-term health outcomes and medical effects of torture among US Navy prisoners of war in Vietnam.

OBJECTIVE: To characterize incidence of illnesses and injuries from 1979 to 1993 in former naval aviator prisoners of war (POWs) from the Vietnam War and a comparison group of naval aviators from the same war. DESIGN: Cohort analytic study. SETTING: A US Navy primary care clinic. PARTICIPANTS: Volunteer sample consisting of 70 former naval aviator POWs (white men, aged 47 to 69 years in 1993) and a comparison group of 55 naval aviators who served in Vietnam but were not POWs, matched on race, age, marital status, education, rank, year of entry into the navy, and pilot status. Subjects participated in an annual health screening program. This study reports data sampled on a biennial basis from subjects screening both in 1979 and 1993. MAIN OUTCOME MEASURE: Medically diagnosed incidence of illness and injury based on a standard protocol. RESULTS: POWs had higher incidence rates than the comparison group did of disorders of the peripheral nervous system (relative risk [RR], 8.4; 95% confidence interval [CI], 2.7-25.9; P<.001), joints (RR, 1.5; 95% CI, 1.2-2.0; P<.006), and back RR, 1.8; 5% CI, 1.0-3.0; P<.037). These findings also were statistically significant according to Kaplan-Meier survival analyses that included 131 (95%) of 138 POWs and 115 (83%) of the 138 members of the comparison group. Survival analyses revealed that, in addition to these disorders, POWs had higher hazard rates of peptic ulcer (P<.01). CONCLUSIONS: During captivity, ropes, ratchet handcuffs, leg irons, or stocks were used to put tightly constrictive pressure around the extremities of POWs as a means of torture, resulting in painful ischemia and subsequent neuropathies. Being a former POW was associated with increased cumulative incidence rates of chronic disorders of the peripheral nervous system, joints, and back and an increased hazard rate of peptic ulcer.

Orthopedic injuries experienced by U.S. prisoners of war during Operation Desert Storm: a descriptive analysis.

U.S. prisoners of war from Operation Desert Storm suffered significant orthopedic injuries. The repatriated prisoners of war (RPOWs) have been medically evaluated over a 3-year period with orthopedic follow-up. A significant proportion of the musculoskeletal injuries were located around the neck and spine, shoulder, and upper extremity. Aircraft ejection was the cause of the majority of these injuries. Lower extremity injuries after ejection, aside from the knee, were not reported. Flail injuries of the lower extremities were absent as well. These results were examined with reference to Vietnam RPOW data.

Compulsive personality traits affecting aeronautical adaptability in a naval aviator: a case report.

This is a case report of a male naval aviator who demonstrated compulsive personality traits which adversely affected the performance of his duties as a pilot trainee, and later, as a naval flight officer. The Diagnostic and Statistical Manual of the American Psychiatric Association (DSM-III-R) uses the term obsessive-compulsive to describe two conditions. A review of terminology is undertaken to present the reader with the distinguishing features of the personality disorder versus the anxiety disorder. The anxiety disorder, obsessive-compulsive disorder, is incompatible with safe performance of aviation duties. Obsessive-compulsive personality, on the other hand, describes a point on a continuum where useful, adaptive compulsive traits may become abnormally exaggerated and maladaptive, thus interfering with the aviator's normal routine, occupational functioning, relationships with others, and aviation safety.

Brief reactive psychosis in naval aviation.

Five naval aviation personnel diagnosed with brief reactive psychosis (BRP) have appeared before the Special Board of Flight Surgeons (SBFS) at the Naval Aerospace Medical Institute (NAMI). These cases demonstrate the challenges in diagnosis and disposition that face the clinical aeromedical specialist in evaluating the aviator who develops psychiatric symptoms. We discuss the aeromedical factors that must be considered when contemplating returning aviators with psychiatric diagnoses to flying duties. Sudden behavioral changes in aviation personnel require a systematic assessment, thorough documentation, and continuing reevaluation. The differentiation between organic and functional etiologies may be difficult. Final disposition may require consultation with experienced physicians skilled in both aviation psychiatry and neurology.

Adult children of alcoholics--a treatable entity: an aviation case report.

This is a case report of a male naval aviator, raised in an alcoholic environment, and the impact of that environment on his development and adult functioning. A review of the adult children of alcoholics syndrome is presented to help familiarize the reader with this evolving entity and its probable impact on aviation personnel. In the United States, current estimates indicate that parental alcoholism affects 27 million children. Only about 5% of these children are receiving any evaluation, supportive care, or treatment. This case of a naval aviator affected by this syndrome illustrates the need for its recognition and potential for treatment and modification of maladaptive behavior. As a treatment entity, recognition of the adult children of alcoholics syndrome will hopefully have a positive effect upon aviation safety and will help save a valuable national asset, our trained aviation personnel.