Evaluation of the robustness of polarization attraction for 10.7-GBaud NRZ-BPSK after long-haul 100-GHz DWDM transmission.

An investigation was carried out on the polarization attraction (PA) of a polarization-scrambled 10.7-GBaud NRZ-BPSK signal in a 1-km-long highly nonlinear fiber (HNLF). For the back-to-back case, PA on an ASE-loaded signal yielded a receiver sensitivity penalty of ≈ 14.5 dB at the ITU-T G.975.1.I3 FEC threshold of 3.5 × 10-3, relative to matched-filter reception theory. After long-haul 100-GHz DWDM transmission in a recirculating loop, PA on the output signal was found to achieve approximately the same receiver sensitivity performance, as that of the back-to-back case. From these experiments, it is concluded that the Gordon-Mollenauer effect due to propagation in the HNLF during PA dominates other impairments including those arising from the long-haul 100-GHz DWDM recirculating loop transmission.

Polarization attraction of 10-Gb/s NRZ-BPSK signal in a highly nonlinear fiber.

Polarization attraction of a 10-Gb/s non-return-to-zero binary phase-shift keyed (NRZ-BPSK) signal has been successfully demonstrated for the first time in a counter-propagating beam configuration using a continuous-wave pump, in a highly nonlinear fiber, by utilizing the Kerr nonlinear cross-polarization process inherent to that fiber. The efficacy of mitigating polarization-dependent loss across polarization-sensitive devices was emulated with a linear polarizer located before the receiver. The receiver sensitivity penalty at 10-9 bit-error-rate relative to the baseline NRZ-BPSK signal was < 0.5 dB, when polarization attraction was employed for a polarization-scrambled signal (after achieving a degree of polarization > 90%). The results confirm that polarization attraction is independent of modulation format.

Higher incidence of HCV in females compared to males who inject drugs: A systematic review and meta-analysis.

Women who inject drugs have been shown to have higher incidence of HIV and risk behaviours than men, but there are conflicting reports about hepatitis C virus (HCV) incidence. We systematically reviewed the literature to examine the female-to-male (F:M) HCV incidence in female and male persons who inject drugs (PWID), and also to explore the heterogeneity (i.e. methodological diversity) in these differences. We searched PubMed and EMBASE for studies published between 1989 and March 2015 for research that reported incidence of HCV infection by sex or HCV incidence F:M rate ratio. A total of 28 studies, which enrolled 9325 PWID, were included. The overall pooled HCV incidence rate (per 100 person-years observation) was 20.36 (95% CI: 13.86, 29.90) and 15.20 (95% CI: 10.52, 21.97) in females and males, respectively. F:M ratio was 1.36:1 (95% CI: 1.13, 1.64) with substantial heterogeneity (I-squared=71.6%). The F:M ratio varied by geographic location from 4.0 (95% CI: 1.80, 8.89) in China to 1.17 (95% CI: 0.95, 1.43) in the U.S. In studies which recruited participants from community settings, the F:M ratio was 1.24 (95% CI: 1.03, 1.48), which was lower than that reported in the clinical settings (1.72, 95% CI: 0.86, 3.45). The number of studies included provided sufficient statistical power to detect sex differences in this analysis. Our findings raise questions and concerns regarding sex differences with respect to the risk of HCV. Both behavioural and biological studies are needed to investigate causes and potential mechanisms as well as sex-specific prevention approaches to HCV infection.

Polarization-insensitive all-optical dual pump-phase transmultiplexing from 2 × 10-GBd OOKs to 10-GBd RZ-QPSK using cross-phase modulation in a birefringent nonlinear PCF.

Polarization-insensitive (PI) all-optical dual pump-phase transmultiplexing from 2 × 10-GBd OOKs to 10-GBd RZ-QPSK was successfully demonstrated in a birefringent nonlinear photonic crystal fiber (PCF), by utilizing cross-phase modulation (XPM) and the inherent birefringence of the device, for the first time. PI operation was achieved by launching the probe and one pump off-axis while the state of polarization (SOP) of the other pump was randomized. Optimum pump-probe detuning, all within the C-Band, was also utilized to reduce the polarization-induced power fluctuation. Receiver sensitivity penalty at 10-9 bit-error-rate was < 5.5 dB in PI operation, relative to the FPGA-precoded RZ-DQPSK baseline.

All-optical amplitude-phase transmultiplexing of RZ-OOK and RZ-BPSK to RZ-QPSK by polarization-insensitive XPM using a nonlinear birefringent AlGaAs waveguide.

Polarization-insensitive (PI) phase-transmultiplexing (PTM) of a 10-Gb/s return-to-zero ON-OFF keying (RZ-OOK) pump and a 10-Gb/s RZbinary phase-shift keying (RZ-BPSK) probe to 20-Gb/s RZ-quadrature-PSK (RZ-QPSK) has been successfully demonstrated for the first time in a passive, birefringent AlGaAs waveguide, utilizing PI cross-phase modulation (PI-XPM). For differential QPSK (DQPSK)-detection, a 10 − 9-BER pre-amplified receiver sensitivity penalty of ≈ 2.5 dB for the in-phase component and ≈ 4.9 dB for the quadrature component were found. The penalties were relative to the FPGA-precoded RZ-DQPSK baseline for a pump-probe detuning of ≈ 12 nm, when the probe state of polarization was scrambled and the pump was launched off-axis into the waveguide.

Spurious mode reduction in dual injection-locked optoelectronic oscillators.

Optoelectronic oscillators (OEOs) are promising sources of low phase noise radio frequency (RF) signals. However, at X-band frequencies, the long optical fiber delay line required for a high oscillator Q also leads to spurious modes (spurs) spaced too narrowly to be filtered by RF filters. The dual injection-locked OEO (DIL-OEO) has been proposed as a solution to this problem. In this work, we describe in detail the construction of a DIL-OEO. We also present experimental data from our systematic study of injection-locking in DIL-OEOs. With this data, we optimize the DIL-OEO, achieving both low phase noise and low spurs. Finally, we present data demonstrating a 60 dB suppression of the nearest-neighbor spur without increasing the phase noise within 1 kHz of the 10 GHz central oscillating mode.

Theoretical investigation of polarization-insensitive data format conversion of RZ-OOK to RZ-BPSK in a nonlinear birefringent fiber.

Polarization-insensitive conversion of return-to-zero (RZ) ON-OFF keying (RZ-OOK) to RZ binary phase-shift keying (RZ-BPSK) has been achieved by cross-phase modulation (XPM) in a nonlinear birefringent fiber. This work presents a theoretical analysis of the dependence of format conversion on pump-probe detuning, and the pump state-of-polarization (SOP) that can fluctuate unpredictably in a realistic system. An investigation of the impact of pump polarization fluctuation on receiver sensitivity and receiver optimal threshold for the converted RZ-BPSK probe is also carried out. It was found that although the desired XPM-induced pi phase shift can be achieved by launching both the RZ-OOK pump and the probe along the same birefringent axis of the fiber, the phase shift degrades to pi/3 if the SOP of the RZ-OOK pump unpredictably switches to the other axis of the fiber, resulting in a large receiver sensitivity penalty fluctuation of 14 dB. By contrast, launching the probe at 45 degrees relative to the birefringent axes can reduce the polarization-dependent receiver sensitivity penalty fluctuation to about 2 dB as the SOP of the RZ-OOK pump is swept over the Poincaré sphere. These conclusions are in good agreement with recently.

Polarization-insensitive, 40 Gb/s wavelength and RZ-OOK-to-RZ-BPSK modulation format conversion by XPM in a highly nonlinear PCF.

Polarization-insensitive wavelength conversion, as well as the conversion of return-to-zero (RZ) ON-OFF keying (RZ-OOK) to RZ binary phase-shift keying (RZ-BPSK), has been simultaneously achieved at 40 Gb/s for the first time by cross-phase modulation (XPM) in a highly birefringent, nonlinear photonic crystal fiber (PCF). A 10-9-BER receiver sensitivity conversion penalty of < 3 dB was achieved for a polarization scrambled, 40 Gb/s 25%-RZ-OOK pump, when the 40 Gb/s RZ probe was launched at 45 degrees with respect to the birefringence axes of the PCF and when the pump-probe detuning was greater than about 6 nm.

The Postgraduate Diploma in Clinical Dental Technology.

The Dental Act 1988 included requirements for the registration of clinical dental technicians, a new category of dental health worker. Despite the Act containing provision for a course of training in clinical dental technology, 11 years elapsed before the first candidates would graduate in this discipline. This paper describes the development and implementation of the new Postgraduate Diploma in Clinical Dental Technology, PGDipCDTech(Otago). Diplomates of the inaugural course in 1999 were the first students, other than students of dentistry, to obtain a clinical qualification from the School of Dentistry. Overall the course was very successful, but the provisions of the Dental Act inhibit flexible approaches to the teaching of clinical dental technology.

A clinically detailed risk information system for cost.

The authors discuss a system that describes the resources needed to treat different subgroups of the population under age 65, based on burden of disease. It is based on 173 conditions, each with up to 3 severity levels, and contains models that combine prospective diagnoses with retrospectively determined elements. We used data from four different payers and standardized the cost of most services. Analyses showed that the models are replicable, are reasonably accurate, explain costs across payers, and reduce rewards for biased selection. A prospective model with additional payments for birth episodes and for serious problems in newborns would be an effective risk adjuster for Medicaid programs.

novel Award First Prize Paper. Orthotic management of plantar pressure and pain in rheumatoid arthritis.

OBJECTIVE: To investigate the effectiveness of foot orthoses in the management of plantar pressure and pain in subjects with rheumatoid arthritis. DESIGN: A repeated measures study in which the independent variable was orthosis design. Dependent variables, including pressure, gait and pain parameters, were examined using analysis of variance and correlation statistics. BACKGROUND: The aim of orthotic management of the rheumatoid foot is to relieve metatarsalgia through the reduction of metatarsal head pressure. Few studies have investigated the relative effectiveness of different orthosis designs. To date, no studies have examined the relationship between plantar pressure and second metatarsal head pain in rheumatoid arthritis subjects. METHODS: Twelve rheumatoid arthritis subjects with foot involvement and second metatarsal head pain were tested. Four styles of foot orthosis (prefabricated, standard custom moulded, custom with metatarsal bar, custom with metatarsal dome) were compared to a shoe only control. An EMED Pedar system was used to measure plantar pressure during repeated trials of comfortable cadence walking and quiet standing. Reports of subjective pain were recorded for each orthosis as were orthosis preferences. RESULTS: All orthoses significantly reduced pressure beneath the first and second metatarsal heads compared to the shoes only control. The custom moulded orthosis with metatarsal dome was the most effective orthosis for reducing subjective ratings of pain. A significant correlation (r=0.562) was found between ratings of pain and average pressure beneath the second metatarsal head. CONCLUSIONS: Results from this study suggest that average pressure measurement may be a useful indicator in the management of metatarsalgia in RA. Further study is required to improve understanding of the relationship between rheumatoid foot mechanics and pain. RELEVANCE: Appropriate foot orthosis design can substantially improve comfort in RA patients with symptomatic feet. A custom moulded foot orthosis incorporating a metatarsal dome was the most effective design for subjects with painful second metatarsal heads. Foot pressure measurement technology can be a useful adjunct to research and clinical management of the painful rheumatoid foot.

Where is the financial safety net for managed care physicians?

OBJECTIVE: Empiric research on mechanisms by which managed care physicians attempt to mitigate financial risk is lacking. We assumed the perspective of a managed care plan in investigating the relationship between risk sharing and the match between a physician's capitation payments and costs of care. DESIGN: The study design was a family of payment simulations using 2 years of managed care claims data. METHODS: Claims from a cohort of 82,525 managed care patients were used, with year 1 data determining a capitation rate for year 2 primary care services. The net provider payment in year 2 was examined under scenarios that might modify financial outcomes, including stop-loss insurance, age- and gender-adjustment of capitation, and risk pooling within independent practice associations. RESULTS: The size of a provider's patient panel was positively correlated with net per capita payment (r = 0.22; P < 0.0001 without risk modification strategies). The variance of the ratio of net to total revenue was utilized as a proxy for the degree of risk assumed in caring for a panel of capitated enrollees. Risk modification strategies reduced this variance measure, with risk pooling producing the largest effect, especially for providers of panels of fewer than 135 patients. In contrast, age- and gender-adjustment of capitation payments had little effect on reimbursement outcomes. CONCLUSIONS: Short of increasing the pool of capitated patients, risk modification strategies appear limited in their ability to produce more equitable reimbursement to providers with small patient panels. With many providers assuming substantial risk in pursuing managed care contracts, these dynamics may favor organizational forms of medical practice that facilitate large patient panels within a single plan.

Factors influencing the retention of cemented implant-supported crowns.

This study is a retrospective analysis of the influence of cement, coping type, and fixture site on the cementation failure of 36 selected implant-supported single crowns placed between 1991 and 1995. Fisher's exact test and a log linear analysis were performed on the data. Crowns constructed with a milled-metal coping, cemented with a temporary cement, or placed in the maxillary premolar site were more likely to be associated with cement failure than those cemented with zinc phosphate, constructed with cast metal or ceramic copings, or placed in the anterior maxilla. We were unable to account for some variables-for example, bite force or oral habits. For this reason we consider that we would overstate the strength of this case analysis if we drew general conclusions from our results. However, we have altered our treatment protocol to reduce the initial cost and the maintenance associated with recementing implant-supported crowns, discontinuing the use of the milled-gold cylinder in view of the lack of any clear clinical advantage and the results of this study. In addition, and because only one internal gold screw in our series of patients has loosened, we now use a permanent cement.

Variations in cataract extraction rates in Medicare prepaid and fee-for-service settings.

OBJECTIVE: To compare rates of cataract extraction in 2 prepaid health settings and in traditional fee-for-service (FFS) settings. DESIGN: A cross-sectional analysis using 1993 health maintenance organization (HMO) Medicare claims and encounter files, the Health Care Financing Administration (HCFA) 5% Medicare Part B provider/supplier file, and the HCFA October 1992 100% Medicare population file. SETTING: Southern California Medicare FFS settings and the staff-model and independent practice association (IPA) plans of a large California HMO. PATIENTS: 1993 Medicare beneficiaries aged 65 years and older. The study included 43387 staff-model HMO enrollees, 19050 IPA enrollees, and 47 150 FFS beneficiaries (a 5% sample of all Southern California FFS beneficiaries). MAIN OUTCOME MEASURE: Age and risk-factor adjusted rates of cataract extraction per 1000 beneficiary-years. RESULTS: After controlling for age, sex, and diabetes mellitus status, FFS beneficiaries were twice as likely to undergo cataract extraction as were prepaid beneficiaries (P<.01). Female FFS beneficiaries were nearly twice as likely to undergo the procedure as were male FFS beneficiaries (P<.001); there were no extraction rate differences by sex in the prepaid settings. CONCLUSION: Because of the potential implications for vision care in the elderly, the significantly different rates of cataract extraction in FFS and prepaid settings warrant further clinical investigation to determine whether there is overuse in FFS vs underuse in prepaid settings. Such investigations must assess the appropriateness of cataract surgery by evaluating its use relative to clinical need.

Timing-jitter reduction for a dispersion-managed soliton system: experimental evidence.

We have measured the timing jitter for dispersion-managed solitons in a recirculating loop for distances up to 20,000 km. The data were obtained with modulated data, 2(7) - 1 and 2(23) - 1 pseudorandom binary sequence patterns, at 10-Gbit/s rates and with an unmodulated pulse train at 10 GHz. We have obtained good agreement with our data, using a filtered Gordon-Haus model for the timing jitter reduced by the energy enhancement of our solitons relative to solitons in a fiber with a constant dispersion equal to our map's path-average dispersion. We have also measured a bit-error rate of <10(-9) at a distance of 15,000 km.

Dispersion-managed solitons in a fiber loop with in-line filtering.

We investigate both numerically and experimentally soliton propagation in a fiber loop with dispersion management, in-line filters, and frequency shifting. More than 90% of the fiber in the loop is in the normal-dispersion regime, but the net dispersion is anomalous. Stable pulses in the loop have an enhanced power relative to solitons in a fiber with uniform dispersion equal to the loop's path-averaged dispersion. Because the loop's path-averaged dispersion is small, the in-line filtering and the frequency shifting play an important role in pulse shaping. Recirculating loop experiments that demonstrate stable pulse propagation over 28,000 km are consistent with results from computer modeling.

Modified capitation and treatment incentives for end stage renal disease.

This study developed a modified capitation payment method for the Medicare end stage renal disease (ESRD) program designed to support appropriate treatment choices and protect health plans from undue financial risk. The payment method consists of risk-adjusted monthly capitated payments for individuals on dialysis or with functioning kidney grafts, lump sum event payments for expected incremental costs of kidney transplantations or graft failures, and outlier payments for expensive patients. The methodology explained 25 percent of variation in annual payments per patient. Risk adjustment captured substantial variations across patient groups. Outlier payments reduced health plan risk by up to 15 percent.

Stress relaxation properties of human dentin.

OBJECTIVES: This study compared the stress relaxation properties of moist and air-dried human dentin to determine if air drying modifies this mechanical property. METHODS: Cylindrical dentin specimens, prepared from human canine and maxillary incisor teeth, were subjected to a controlled compressive stress applied at a constant strain rate to a predetermined maximum value, and the stress relaxation response recorded. Groups of moist and air-dried specimens were tested at both low and high stress. After a period of 1 wk, the incisor specimens were retested. RESULTS: The dentin exhibited a linear stress relaxation with the logarithm of time. Air-dried dentin consistently demonstrated a decreased stress relaxation. When subjected to a second high load, the air-dried dentin displayed significantly slower stress relaxation. Air-dried incisor dentin was found to be significantly stiffer than air-dried canine dentin. SIGNIFICANCE: These data suggest that the stress relaxation properties of human dentin are modified by air drying and by previous exposure to a constant compressive strain.