Importance sampling for polarization-mode dispersion

We describe the application of importance sampling to Monte-Carlo simulations of polarization-mode dispersion (PMD) in optical fibers. The method allows rare differential group delay (DGD) events to be simulated much more efficiently than with standard Monte-Carlo methods and, thus, it can be used to assess PMD-induced system outage probabilities at realistic bit-error rates. We demonstrate the technique by accurately calculating the tails of the DGD probability distribution with a relatively small number of Monte-Carlo trials     

Testing to predict outcome after transurethral resection of the prostate

PURPOSE: We assessed the ability of routine clinical tests to predict outcome following transurethral resection of the prostate. MATERIALS AND METHODS: A total of 556 men randomized into a trial of surgery versus watchful waiting was evaluated preoperatively with symptom interview, quality of life assessment, uroflowmetry, urinalysis, standard chemistry panel, post-void residual urine determination and cystoscopy. The ability to predict avoidance of postoperative complications, and improvement in quality of life and genitourinary symptoms was assessed in the 249 men randomized to undergo transurethral resection of the prostate. RESULTS: Patients with the highest symptom scores were most likely to have symptom improvement and those most bothered by the symptoms were most likely to have improvement in quality of life. No objective tests measuring physiological parameters made clinically significant contributions toward predicting these outcomes. Lower obstructive symptom scores and larger perioperative infusions of intravenous fluids were associated with a greater chance of complications. CONCLUSIONS: Symptom analysis and quality of life assessment are most useful in selecting patients for transurethral resection of the prostate. Objective diagnostic tests are of limited additional benefit.     

Accurate calculation of eye diagrams and bit error rates in opticaltransmission systems using linearization

We present a novel linearization method to calculate accurate eye diagrams and bit error rates (BERs) for arbitrary optical transmission systems and apply it to a dispersion-managed soliton (DMS) system. In this approach, we calculate the full nonlinear evolution using Monte Carlo methods. However, we analyze the data at the receiver assuming that the nonlinear interaction of the noise with itself in an appropriate basis set is negligible during transmission. Noise-noise beating due to the quadratic nonlinearity in the receiver is kept. We apply this approach to a highly nonlinear DMS system, which is a stringent test of our approach. In this case, we cannot simply use a Fourier basis to linearize, but we must first separate the phase and timing jitters. Once that is done, the remaining Fourier amplitudes of the noise obey a multivariate Gaussian distribution, the timing jitter is Gaussian distributed, and the phase jitter obeys a Jacobi-Θ distribution, which is the periodic analogue of a Gaussian distribution. We have carefully validated the linearization assumption through extensive Monte Carlo simulations. Once the effect of timing jitter is restored at the receiver, we calculate complete eye diagrams and the probability density functions for the marks and spaces. This new method is far more accurate than the currently accepted approach of simply fitting Gaussian curves to the distributions of the marks and spaces. In addition, we present a deterministic solution alternative to the Monte Carlo method     

Integration of on-line quality control into the process control environment for cheese manufacturing

This paper outlines the development of an interactive on-line quality control system for a cheese manufacturing process. The system consists of an Access^® database with a graphical user interface developed in Visual Basic. The database resides on a Digital MicroVAX server, linked to PC's running Pathworks for Windows 95 across a Local Area Network. The system facilitates the rapid and accurate revision and updating of the ISO manual, which saves time, money and resources. With the increase in data available, areas in the process procedure such as sensor monitoring which would traditionally have an independent role can now be fully integrated into the manufacturing process. The current project takes advantage of this fact and integrates the Quality Control Procedures into the on-line process control, thus enhancing adherence to ISO standards. The system increases operator empowerment by providing the operator with the necessary information and decision support mechanism to react to a situation in a consistent and appropriate manner. This approach to quality control monitoring and implementation is a significant improvement over the standard and rather static quality control manuals utilised at present.     

Identification and bioassay of sex pheromone components of carob moth,Ectomyelois ceratoniae (Zeller)

Three sex pheromone components of the carob moth were isolated and identified from the extract of female pheromone glands, using a variety of techniques including coupled gas chromatographic-electroantennographic recordings, coupled gas chromatographic-mass spectrometric analysis, microozonolysis, electroantennographic assays of monounsaturated standards, wind-tunnel bioassays, and field trials. The major component was identified as (Z,E)-9,11,13-tetradecatrienal, a novel lepidopterous pheromone component structure. Two minor components, either one of which improves the upwind flight response of males when blended with the major component, were identified as (Z,E)-9,11-tetradecadienal, and (Z)-9-tetra-decenal.     

Comparison of cytotoxic action of iphosphamide and cyclophosphamide

We compared the cytotoxic effects of cyclophosphamide and iphosphamide on normal hematopoietic colony-forming units (NCFU) and L1210 leukemia colony-forming units (LCFU), using the quantitative spleen colony assay. Cyclophosphamide was more cytotoxic for NCFU than iphosphamide, but both agents had a similar cytotoxic effect on LCFU survival, whether given as a single injection or a 24-hour infusion. Although both agents were less cytotoxic for LCFU when administered in 24-hour infusions, host toxicity indicated that correspondingly larger doses of each agent could be given by infusion. The two agents also exhibited very similar cell-killing kinetics.     

Full-Scale Measurements to Investigate Rain–Wind Induced Cable-Stay Vibration and Its Mitigation

Large-amplitude vibrations are known to occur in the main stays of cable-stayed bridges in the presence of rain and wind. Although this problem first surfaced in many bridges around the world in the mid-1980s, it was not until 1996 when the Texas Department of Transportation began to investigate this problem in the United States. Both wind-tunnel and full-scale tests were conducted simultaneously to better understand this phenomenon and devise mitigation methods to reduce the vibrations. Full-scale tests were conducted on four cable stays of the Veterans’ Memorial Bridge near Port Arthur, Tex., over a period of three years. This paper presents observations from selected full-scale data and compares them to wind-tunnel test results as well as results found in past literature. Some observations regarding assessment of a distributed passive mitigation device that was installed on one of the cable stays in the field to control vibrations in the presence of rain and wind are also presented. Wind-tunnel tests show that this device is very effective. Limited data collected from the field after the installation of the device gives some evidence of its effectiveness in reducing the vibrations.     

Statistical analysis of the performance of PMD compensators using multiple importance sampling

In this letter, we evaluate the performance of fixed and variable differential group delay (DGD) polarization-mode dispersion (PMD) compensators as the first- and second-order PMD varies using multiple importance sampling. We show that importance sampling yields estimates of the average penalty with low variance over the entire region of interest of first- and second-order PMD. We also show that there is little advantage in using a compensator with a variable-DGD element and that the performance of a compensator that minimizes the residual DGD at the central frequency of the channel is considerably worse than a compensator that maximizes the eye opening.     

Does the onset of neonatal seizures correlate with the timing of fetal neurologic injury?

The onset of seizures after birth has been considered evidence of an intrapartum asphyxial event. The present study was undertaken to determine whether the timing of neonatal seizures after birth correlated with the timing of a fetal asphyxial event. Thus, singleton term infants diagnosed with hypoxic ischemic encephalopathy and permanent brain injury had a mean birth to seizure onset interval of 9.8 +/- 17.7 (range 1-90) hours. When these infants were categorized according to their fetal heart rate (FHR) patterns, the acute group (normal FHR followed by a sudden prolonged FHR deceleration that continued until delivery) tended to have earlier seizures than infants did within the tachycardia group (normal FHR followed by tachycardia, repetitive decelerations, and diminished variability) and the preadmission group (persistent nonreactive FHR pattern intrapartum). These seizure intervals were as follows: acute, 6.6 +/- 18.0 (range 1-90) hours; tachycardia, 11.1 +/- 17.1 (range 1-61) hours; and preadmission, 11.8 +/- 17.9 (range 1-79) hours (p < 0.05). But the range varied widely and no group was categorically distinct. In conclusion, the onset of neonatal seizures after birth does not, in and of itself, appear to be a reliable indicator of the timing of fetal neurologic injury.