Precision spectral sculpting for narrow-band amplification of broadband frequency-modulated pulses.

Amplification of broadband frequency-modulated (FM) pulses in high-efficiency materials such as ytterbium-doped strontium fluorapatite results in significant gain narrowing, leading to reduced on-target bandwidths for beam smoothing and to conversion from frequency modulation to amplitude modulation (AM). To compensate for these effects, we have applied precision spectral sculpting, requiring both amplitude and phase shaping, to the amplification of broadband FM pulses in narrow-band gain media. We have demonstrated sculpting for centerline small-signal gains of 10(4), producing amplified pulses that have both sufficient bandwidths for on-target beam smoothing and temporal profiles that have no potentially damaging AM.

Hematometra after thermal balloon endometrial ablation in a patient with cervical incompetence.

BACKGROUND: Thermal balloon endometrial ablation is a relatively safe nonsurgical treatment for menorrhagia. Hematometra follows this procedure in <3 % of patients, but risk factors for this complication are unclear. CASE: A woman with a history of cervical incompetence during pregnancy later developed cervical occlusion and hematometra after thermal balloon endometrial ablation. Cervical occlusion did not recur after cervical dilatation and temporary placement of a catheter as a stent. CONCLUSION: The normal resistance of the internal cervical os may be an important factor in avoiding thermal damage to the cervix during thermal balloon endometrial ablation. This case suggests that a history of cervical incompetence may be a clinical indicator of decreased cervical resistance.

Vaginal bleeding from massive hemoperitoneum. A case report.

BACKGROUND: A gynecology service is often asked to consult and evaluate in-house patients with vaginal bleeding. CASE: A 31-year-old, Asian woman with a history of end-stage renal disease and hemodialysis was admitted to the hospital with a falling hematocrit. She subsequently began to have heavy vaginal bleeding. Computed tomography suggested a peritoneal-cervical fistula. Subsequent exploratory laparotomy documented that the bleeding was caused by retrograde flow of a hemoperitoneum. CONCLUSION: This appears to be the first reported case of retrograde flow from a hemoperitoneum causing vaginal bleeding. Although unusual, this case expands the differential diagnosis when evaluating vaginal bleeding.

Concurrent substance use and outcome in combined behavioral and naltrexone therapy for opiate dependence.

UNLABELLED: The effect of concurrent nonopiate drug use on outcome of treatment for opiate dependence. METHOD: Forty-seven opiate-dependent patients received a 6-month course of outpatient treatment with naltrexone and cognitive-behavioral therapy (behavioral naltrexone therapy, BNT) at a university-based research clinic. Opiate-negative urines and naltrexone ingestion were rewarded with monetary vouchers. Abstinence from other drugs was encouraged verbally, but no contingencies were placed on nonopiate drug use. The proportions of all urines (collected twice weekly) positive for cocaine, cannabis, and benzodiazepines over the course of treatment were evaluated as predictors of outcome of opiate dependence treatment, as measured by proportion of opiate-positive urines, days retained in treatment, and proportion of naltrexone doses taken, using Pearson product moment correlations and one-way analysis of variance (ANOVA). RESULTS: The majority of patients (78%) used a nonopiate drug at least once during the trial. There were no significant correlations between concurrent drug use measures and opiate dependence treatment outcomes, indicating no simple linear relationship between these measures. However, when concurrent drug use was trichotomized into abstinent, intermittent, and heavy use groups, groups with intermittent use had superior outcome compared to both abstinent and heavy use groups in several contrasts. CONCLUSIONS: Intermittent use of nonopiate drugs is common during outpatient treatment for opiate dependence and may be a favorable prognostic indicator. This may support a "harm reduction" approach as opposed to a strict abstinence-oriented approach. Further research is needed to identify the optimal therapeutic stance toward other drug use during treatment for opiate dependence.

Backscatter reduction using combined spatial, temporal, and polarization beam smoothing in a long-scale-length laser plasma.

Spatial, temporal, and polarization smoothing schemes are combined for the first time to reduce to a few percent the total stimulated backscatter of a NIF-like probe laser beam (2x10(15) W/cm (2), 351 nm, f/8) in a long-scale-length laser plasma. Combining temporal and polarization smoothing reduces simulated Brillouin scattering and simulated Raman scattering (SRS) up to an order of magnitude although neither smoothing scheme by itself is uniformly effective. The results agree with trends observed in simulations performed with the laser-plasma interaction code F3D simulations [R. L. Berger et al., Phys. Plasma 6, 1043 (1999)].

Ultrafast picket fence pulse trains to enhance frequency conversion of shaped inertial confinement fusion laser pulses.

A high-frequency train of 5-100-ps pulses (picket fence) is proposed to improve significantly the third-harmonic frequency conversion of Nd:glass lasers that are used to generate high-contrast-shaped pulses for inertial confinement fusion (ICF) targets. High conversion efficiency of the low-power foot of a shaped ICF pulse is obtained by use of a low duty cycle, multi-gigahertz train of approximately 20-ps pulses with high peak power. Even with less than 10% duty cycle, continuous illumination is maintained on the target by a combination of temporal broadening schemes. The picket fence approach is analyzed, and the practical limits are identified as applied to the National Ignition Facility laser. It is found that the higher conversion efficiency allows approximately 40% more third-harmonic energy to be delivered to the target, potentially enabling the larger drive needed for high-yield ICF target designs. In addition, the frequency conversion efficiency of these short pulses saturates much more readily, which reduces the transfer of fluctuations at the fundamental and thus greatly improves the power stability of the third harmonic.

Occult bladder injury during laparoscopy: report of two cases.

Bladder injuries occur in approximately 1.6% of all laparoscopic procedures. Most often, these injuries are recognized intraoperatively or immediately postoperatively because of gross hematuria. We report two cases of bladder injury related to placement of suprapubic laparoscopic trocars that were not recognized at the time of surgery and in which no gross hematuria was evident. In each case, the patient had a history of abdominal surgery, and the diagnosis was difficult to make. The treatment was prolonged catheterization in one patient and laparotomy through a midline incision in the other. Strategies are discussed for minimizing the risk of bladder injury during laparoscopic trocar placement and for diagnosing and treating injuries.

Is a third-trimester antibody screen in Rh+ women necessary?

OBJECTIVE: To determine the need for routine third-trimester antibody screening in Rh+ women. STUDY DESIGN: An analytic case-control study. METHODS: We identified Rh+ pregnant women who had received prenatal care and retrospectively analyzed their laboratory data. Patients were grouped into those with a positive third-trimester antibody screen (cases) and those with a negative third-trimester screen (controls). Because entry into a group was decided by the investigators, it could not be randomized. We reviewed the maternal medical records for antibody identification and final pregnancy outcome. We also reviewed the neonatal medical records for evidence of direct Coombs-positive cord blood, anemia, need for transfusion or phototherapy, other medical complications, and death. RESULTS: Using a computerized laboratory database from 2 teaching hospitals, we identified 10,581 obstetric patients who underwent routine first- and third-trimester antibody screening between 1988 and 1997. Of these, 1233 patients were Rh- and 9348 were Rh+. Among the Rh+ patients, 178 (1.9%) had 1 or more atypical antibodies at the first-trimester screen, and 53 (0.6%) had a positive third-trimester antibody screen despite a negative first-trimester screen. Although 6 of these 53 patients (0.06% of the study population) had clinically relevant antibodies for hemolytic disease of the new-born, no significant neonatal sequelae occurred among these 6 patients. CONCLUSION: Based on the patient and hospital records studied, a repeat third-trimester antibody screen for Rh+ patients is clinically and economically unjustified. Eliminating this laboratory test from clinical practice will not adversely affect pregnancy outcomes and will decrease the costs of prenatal care.

Location of the transverse colon in relationship to the umbilicus: implications for laparoscopic techniques.

STUDY OBJECTIVE: To establish the location of the transverse colon in relationship to the umbilicus, and determine if it varies as a function of patient height or weight. DESIGN: Retrospective review of computed tomograms (CT) of the abdomen (Canadian Task Force classification II-2). SETTING: University hospital. PATIENTS: Sixty-seven women with normal abdominal anatomy. INTERVENTION: Review of abdominal CT scans. MEASUREMENTS AND MAIN RESULTS: The relative relationships of the transverse colon and umbilicus were compared with age, height, weight, and body mass index (BMI = kg/m2) using multiple regression analysis. Average location of the superior margin of the transverse colon was 4.6 cm (95% CI 3.5-5.7 cm) above the umbilicus. In nine (13%) women it was below the umbilicus. The colon was below the umbilicus in 25% of nonobese women (BMI <25 kg/m2). CONCLUSION: Because the transverse colon lies below the umbilicus in more than 10% of women, injury to it may be an uncommon yet unavoidable complication of laparoscopy.

Leg ulceration and the cholesterol embolus.

An important and frequently overlooked cause of leg ulcers are cholesterol emboli. A 79-year-old woman with a non-healing leg ulcer is described. The diagnosis of cholesterol embolism was made with the aid of a deep biopsy of the ulcer and serial sectioning of the specimen. This report serves to illustrate the importance of considering cholesterol embolism when evaluating a chronic leg ulcer, and the diagnostic value of proper biopsy techniques.

Complete all-optical switching of visible picosecond pulses in birefringent fiber.

Switching of visible picosecond pulses with a 50:1 contrast ratio is demonstrated in a time-division interferometry arrangement. The high-contrast switching of the signal is accomplished by uniform cross-phase modulation by an orthogonally polarized control pulse that walks through the signal during propagation in a strongly birefringent 10-m fiber.

Observation of the formation of dark-soliton trains in optical fibers.

We present observations that demonstrate a technique for the generation of trains of dark solitons. The technique consists of the nonlinear copropagation of two delayed visible pulses in a long optical fiber. Single-shot streak-camera temporal images depict the formation of trains of dark solitons with picosecond widths. Single-shot spectra are also observed and depict ringing around spectral holes, which is characteristic of dark solitons on a chirped background pulse. Good agreement is found between theory and both temporal and spectral measurements.

Pulse splitting during self-focusing in normally dispersive media.

The self-focusing of femtosecond optical pulses in a normally dispersive medium is studied numerically. This situation represents a general problem that may be modeled by a 3 + 1-dimensional nonlinear Schrödinger equation, where two dimensions are self-focusing and the third is self-defocusing. The numerical simulations show that the dispersion causes the splitting of a pulse before it self-focuses into two temporally separated pulses, which then continue to self-focus and compress rapidly. The calculated behavior results in periodic modulation of the generated continuum spectrum, as was recently observed in continuum generation by focused femtosecond pulses in gases.

Part 1. Innovations in treating anterior cruciate ligament deficiency.

Orthopaedic clinicians and researchers have made great strides in understanding the intricacy of the anterior cruciate ligament (ACL). The number of ACL injuries is increasing with a more active population and more advanced diagnostic techniques. The ACL's importance for normal knee function has created a great need to find reconstructive techniques that will restore and maintain the complex motion of the knee.

Observation of the buildup of modulational instability from wave breaking.

Orthogonally polarized pulses copropagating in birefringent fiber are observed to develop coherent terahertz intensity oscillations owing to modulational instability. Rather than forming spontaneously from noise with random phase, the modulational instability is coherently initiated from wave-breaking oscillations. This results in stable terahertz oscillations that have little timing jitter from pulse to pulse. Experimentally this is evidenced by the terahertz modulation observed in cross correlations that are obtained by averaged sampling over many pulses. Numerical integrations of coupled nonlinear Schrödinger equations verify this description.