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.

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.

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.

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.

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.

Alterations to mandibular form following motor denervation of the masseter muscle. An experimental study in the rat

The form of the mandible in young rats was studied following denervation of the masseter muscle. Wistar-derived male rats aged 27 d were randomly assigned either to experimental, sham-operated or control groups. The main trunk and initial branches of the masseteric nerve were resected on one side in each experimental animal. The nerve was exposed, but not resected, in the sham-operated group. No surgery was performed on the control group. All animals were killed at 69 d of age, examined and standardised contact radiographs taken of the cleaned and dried mandibles. Radiographic measurements describing the form and size of the mandibles were compared. On the operated side in the experimental animals the masseter muscle was smaller and the temporalis muscle larger as compared with the unoperated side. The angular process and the subcondylar incisure were also smaller and the coronoid process was positioned more rostrally. The most striking feature was that relatively little change accompanied denervation of masseter in the growing experimental rats. It is concluded that some of the changes previously attributed to muscle denervation may be due to other causes.

Six years' experience with Brånemark osseointegrated implants

Over 6 years of the implant programme in the University of Otago School of Dentistry, the rate of use of osseointegrated implants to support or retain a dental prosthesis has increased. This increased use has been most marked in young adults who have required the restoration of a single space in the anterior maxillae. The treatment outcome is unequivocally positive, with an overall fixture retention rate of over 99 percent.

A lifetime-based optical CO2 gas sensor with blue or red excitation and stokes or anti-stokes detection

We describe the fabrication and characterization of an optical CO2 sensor based on the change in fluorescence lifetimes due to fluorescence resonance energy transfer from a pH-insensitive donor, sulforhodamine 101, to a pH-sensitive acceptor, either m-cresol purple or thymol blue, entrapped in an ethyl cellulose film. A phase transfer agent allows incorporation of the dyes and water into the film, while providing an initially basic environment for the acceptor. Diffusion of CO2 into the water entrapped in the film produced carbonic acid, causing a pH-dependent decrease in the spectral overlap of the acceptor absorbance with the donor emission, and decreased energy transfer, resulting in increased SR101 donor lifetimes. The lifetime changes were detected as a change in the phase of the emission, relative to the modulated excitation, and were insensitive to excitation intensities and emission signal levels. In addition to an externally modulated 442-nm light source, we excited the sensor with a directly modulated 635-nm laser diode and detected the anti-Stokes emission. The CO2 sensor is not fragile and can provide stable readings for weeks. The use of fluorescence resonance energy transfer, along with the simple entrainment procedure, allows facile change of the CO2 response range through change of the acceptor dye and the use of laser diode excitation sources.

Implant-based treatment for the loss of a single tooth

This article describes the authors' experience in the provision of single-tooth replacement by means of Brånemark implant treatments. Over a 5-year period, 45 treatments have been undertaken with a current fixture retention rate of 100 percent. Careful planning and attention to detail in surgical, prosthodontic, and technical aspects have resulted in an excellent functional and aesthetic treatment with high acceptance by patients.

Success and failure in partial edentulism treated with implant-supported bridges

This report describes success and failure in the use of fixed bridges supported by Brånemark implants, placed in the mandible bilaterally in one patient and unilaterally in the other. The non-intrusive nature and excellent functional characteristics of such bridges make them an attractive alternative to a removable partial denture in making good the loss of posterior mandibular teeth. However, there are biomechanical principles which must be considered in the design of such appliances. In particular, designs which minimise bending moments should be chosen to avoid the type of failure described in one of our patients. Repeated loosening of screw components should be considered as a possible indicator of bending overload. Where space permits, this problem is most easily overcome by placing three implants in staggered formation.

Use of diagnosis-related groups by non-Medicare payers

Medicare's prospective payment system (PPS) for hospital cases is based on diagnosis-related groups (DRGs). A wide variety of other third-party payers for hospital care have adapted elements of this system for their own use. The extent of DRG use varies considerably both by type of payer and by geographical area. Users include: 21 State Medicaid programs, 3 workers' compensation systems, the Civilian Health and Medical Program of the Uniformed Services (CHAMPUS), more than one-half of the Blue Cross and Blue Shield Association (BCBSA) member plans, several self-insured employers, and a few employer coalitions. We describe how each of these payers use DRGs. No single approach is dominant. Some payers negotiate specific prices for so many combinations of DRG and hospital that the paradigm that payment equals rate times weight does not apply. What has emerged appears to be a very flexible payment system in which the only constant is the use of DRGs as a measure of output.

Fiber-compressed high-repetition-rate pulses from a mode-locked GaAs diode laser

A GaAs diode laser (wavelength 800 nm) was actively mode locked in an external cavity that utilized grating feedback or injection seeding to control the optical spectrum of the pulses and hence the laser's frequency chirp. The chirp was large enough and the pulse duration short enough that the pulses could be compressed in single-mode optical fiber. The shortest pulses were compressed to 7 ps at a 4.1-GHz repetition rate in 550 m of optical fiber, with an average output power of 0.3 mW measured after the pulse compressor.

Fractures and dislocations of fingers and toes. Principles, tips and pitfalls

If each injury is carefully assessed on its merits good outcomes will be achieved. If any kind of unusual situation is met advice should be sought early rather than late. Balancing competing concepts, especially with regard to mobilisation and immobilisation of the injured part, makes treatment of digital injuries a challenge to our ingenuity.

A longitudinal comparison of charge-based weights with cost-based weights

The diagnosis-related group weights that determine prices for Medicare hospital stays are recalibrated annually using charge data. Using data from fiscal years 1985 through 1987, the authors show that differences between these charge-based weights and cost-based weights are increasing only slightly. Charge-based weights are available in a more timely manner and, based on temporal changes in the weights, we show that this is an important consideration. Charge-based weights provide higher payments than cost-based weights to hospitals with higher case-mix indexes, but have little effect on hospitals with low cost-to-charge ratios, high capital costs, or high teaching costs.

Assessing the FY 1989 change in Medicare PPS outlier policy

In fiscal year (FY) 1989, Medicare changed its rules for paying for extremely long or expensive hospital stays called "outliers." We compared outlier payments in FYs 1989 and 1988, after adjusting for other simultaneous policy changes. We found that the new policy succeeded in targeting more outlier payments to the most expensive cases and to the hospitals suffering larger prospective payment system (PPS) losses and in reducing hospital financial risk. Using time-series analyses, we show that the policy change had no measurable effect on the timing of discharges or on the concentration of expensive cases in urban government-owned hospitals.

How recalibration method, pricing, and coding affect DRG weights

We compared diagnosis-related group (DRG) weights calculated using the hospital-specific relative-value (HSRV) methodology with those calculated using the standard methodology for each year from 1985 through 1989 and analyzed differences between the two methods in detail for 1989. We provide evidence suggesting that classification error and subsidies of higher weighted cases by lower weighted cases caused compression in the weights used for payment as late as the fifth year of the prospective payment system. However, later weights calculated by the standard method are not compressed because a statistical correlation between high markups and high case-mix indexes offsets the cross-subsidization. HSRV weights from the same files are compressed because this methodology is more sensitive to cross-subsidies. However, both sets of weights produce equally good estimates of hospital-level costs net of those expenses that are paid by outlier payments. The greater compression of the HSRV weights is counterbalanced by the fact that more high-weight cases qualify as outliers.

How much change in the case mix index is DRG creep?

We re-abstracted a nationally representative sample of 7,887 Medicare charts to determine how much of the change in Medicare's Case Mix Index between 1986 and 1987 was true change in the complexity of cases and how much was upcoding or 'DRG creep'. About two-thirds of the change is true. Most of the remaining third is attributable to a general change in the completeness of coding; some is attributable to changes in the Grouper program. Thus, most of the additional $1 billion paid to hospitals because of the Case Mix Index change appears justified by the additional complexity of patients hospitalized.

Optical spatial tracking using coherent detection in the pupil plane

Design considerations for a heterodyne spatial tracking system utilizing pupil plane processing techniques and its advantages over traditional focal plane processing are described. Noise performance bounds, optimal and suboptimal local oscillator distributions, pull-in performance, and applications other than spatial tracking are discussed. Experimental verification of a one-axis closed-loop tracking system is presented.

Insurance aspects of DRG outlier payments

As part of the prospective payment system, the government pays 'outlier' payments for especially long or expensive cases. These payments can be viewed as insurance for the hospital against excessive losses. They mitigate problems of access and underprovision of care for the sickest patients, and provide additional payments to the hospitals that take care of them, thereby making payments to hospitals more equitable. This paper characterizes the outlier payment formulae that minimize risk for hospitals under any fixed constraints on the sum of outlier payments and minimum hospital coinsurance rate. We then simulate per-case payments for a policy that did not include any outlier payments, the current outlier policy, and several other policies that minimize risk subject to different coinsurance constraints. The current outlier policy achieves each of its goals to at least some extent, but more insurance could be provided without lessening attainment of the other goals. We also discuss some problems with the implementation of the current policy, such as its reliance on day outliers.

Medicare case-mix index increase

Medicare paid hospitals a higher amount per admission in 1984 than had been planned because the case-mix index (CMI), which reflects the proportion of patients in high-weighted DRG's versus low-weighted ones, increased more than had been projected. This study estimated the degree to which the increase in the CMI from 1981 reflected medical practice changes, the aging of the Medicare inpatient population, changes in coding practices of physicians and hospitals, and changes in the way that the Health Care Financing Administration collects the data on case-mix. All of the above, except for aging, contributed to the increase in the CMI.

Oxygen consumption for lower extremity exercises in normal subjects and burned patients

The purpose of this study was to compare the oxygen requirements for normal subjects and burned patients during rest and while performing two separate exercises of the quadriceps femoris muscles. The oxygen consumption of 10 normal subjects and 10 burned patients while at rest and while performing each exercise was measured. The resting and exercising oxygen-consumption levels for burned patients were significantly greater (p < .01) than for normal subjects. However, the mean difference in increased oxygen consumption during two exercises for normal subjects and for burned patients was not significant (p > .05). The elevated resting and exercising oxygen-consumption levels in burned patients were considered to be related to the hypermetabolic response characteristic of thermally injured patients.

Electrooptically Q-switched CO(2) waveguide laser

A flowing-gas CO(2) waveguide laser whose cw output is 13 W has been electrooptically Q-switched repetitively at rates up to 108 kHz and, with a 20% duty cycle, up to 345 kHz. To extract power efficiently in the Q-switched mode, it is necessary to operate the laser at far higher pulse repetition frequencies than for low-pressure lasers. A simplified theory was used to describe this behavior accurately. The short-term (10-msec) frequency stability was measured to be less, similar200 kHz.

Recirculating atomic beam oven

We describe an atomic beam oven that reuses alkali metal in the unused portion of the beam. This is accomplished by condensing the desired vapor on a cooled jacket from which it may be drained back into the oven.