High-threshold and low-overhead fault-tolerant quantum memory

The accumulation of physical errors1-3 prevents the execution of large-scale algorithms in current quantum computers. Quantum error correction4 promises a solution by encoding k logical qubits onto a larger number n of physical qubits, such that the physical errors are suppressed enough to allow running a desired computation with tolerable fidelity. Quantum error correction becomes practically realizable once the physical error rate is below a threshold value that depends on the choice of quantum code, syndrome measurement circuit and decoding algorithm5. We present an end-to-end quantum error correction protocol that implements fault-tolerant memory on the basis of a family of low-density parity-check codes6. Our approach achieves an error threshold of 0.7% for the standard circuit-based noise model, on par with the surface code7-10 that for 20 years was the leading code in terms of error threshold. The syndrome measurement cycle for a length-n code in our family requires n ancillary qubits and a depth-8 circuit with CNOT gates, qubit initializations and measurements. The required qubit connectivity is a degree-6 graph composed of two edge-disjoint planar subgraphs. In particular, we show that 12 logical qubits can be preserved for nearly 1 million syndrome cycles using 288 physical qubits in total, assuming the physical error rate of 0.1%, whereas the surface code would require nearly 3,000 physical qubits to achieve said performance. Our findings bring demonstrations of a low-overhead fault-tolerant quantum memory within the reach of near-term quantum processors.

Encoding a magic state with beyond break-even fidelity

To run large-scale algorithms on a quantum computer, error-correcting codes must be able to perform a fundamental set of operations, called logic gates, while isolating the encoded information from noise1-8. We can complete a universal set of logic gates by producing special resources called magic states9-11. It is therefore important to produce high-fidelity magic states to conduct algorithms while introducing a minimal amount of noise to the computation. Here we propose and implement a scheme to prepare a magic state on a superconducting qubit array using error correction. We find that our scheme produces better magic states than those that can be prepared using the individual qubits of the device. This demonstrates a fundamental principle of fault-tolerant quantum computing12, namely, that we can use error correction to improve the quality of logic gates with noisy qubits. Moreover, we show that the yield of magic states can be increased using adaptive circuits, in which the circuit elements are changed depending on the outcome of mid-circuit measurements. This demonstrates an essential capability needed for many error-correction subroutines. We believe that our prototype will be invaluable in the future as it can reduce the number of physical qubits needed to produce high-fidelity magic states in large-scale quantum-computing architectures.

Demonstrating multi-round subsystem quantum error correction using matching and maximum likelihood decoders

Quantum error correction offers a promising path for performing high fidelity quantum computations. Although fully fault-tolerant executions of algorithms remain unrealized, recent improvements in control electronics and quantum hardware enable increasingly advanced demonstrations of the necessary operations for error correction. Here, we perform quantum error correction on superconducting qubits connected in a heavy-hexagon lattice. We encode a logical qubit with distance three and perform several rounds of fault-tolerant syndrome measurements that allow for the correction of any single fault in the circuitry. Using real-time feedback, we reset syndrome and flag qubits conditionally after each syndrome extraction cycle. We report decoder dependent logical error, with average logical error per syndrome measurement in Z(X)-basis of ~0.040 (~0.088) and ~0.037 (~0.087) for matching and maximum likelihood decoders, respectively, on leakage post-selected data.

Aqueous skin antisepsis before surgical fixation of open fractures (Aqueous-PREP): a multiple-period, cluster-randomised, crossover trial

BACKGROUND

Chlorhexidine skin antisepsis is frequently recommended for most surgical procedures; however, it is unclear if these recommendations should apply to surgery involving traumatic contaminated wounds where povidone-iodine has previously been preferred. We aimed to compare the effect of aqueous 10% povidone-iodine versus aqueous 4% chlorhexidine gluconate on the risk of surgical site infection in patients who required surgery for an open fracture.

METHODS

We conducted a multiple-period, cluster-randomised, crossover trial (Aqueous-PREP) at 14 hospitals in Canada, Spain, and the USA. Eligible patients were adults aged 18 years or older with an open extremity fracture treated with a surgical fixation implant. For inclusion, the open fracture required formal surgical debridement within 72 h of the injury. Participating sites were randomly assigned (1:1) to use either aqueous 10% povidone-iodine or aqueous 4% chlorhexidine gluconate immediately before surgical incision; sites then alternated between the study interventions every 2 months. Participants, health-care providers, and study personnel were aware of the treatment assignment due to the colour of the solutions. The outcome adjudicators and data analysts were masked to treatment allocation. The primary outcome was surgical site infection, guided by the 2017 US Centers for Disease Control and Prevention National Healthcare Safety Network reporting criteria, which included superficial incisional infection within 30 days or deep incisional or organ space infection within 90 days of surgery. The primary analyses followed the intention-to-treat principle and included all participants in the groups to which they were randomly assigned. This study is registered with ClinicalTrials.gov, NCT03385304.

FINDINGS

Between April 8, 2018, and June 8, 2021, 3619 patients were assessed for eligibility and 1683 were enrolled and randomly assigned to povidone-iodine (n=847) or chlorhexidine gluconate (n=836). The trial's adjudication committee determined that 45 participants were ineligible, leaving 1638 participants in the primary analysis, with 828 in the povidone-iodine group and 810 in the chlorhexidine gluconate group (mean age 44·9 years [SD 18·0]; 629 [38%] were female and 1009 [62%] were male). Among 1571 participants in whom the primary outcome was known, a surgical site infection occurred in 59 (7%) of 787 participants in the povidone-iodine group and 58 (7%) of 784 in the chlorhexidine gluconate group (odds ratio 1·11, 95% CI 0·74 to 1·65; p=0·61; risk difference 0·6%, 95% CI -1·4 to 3·4).

INTERPRETATION

For patients who require surgical fixation of an open fracture, either aqueous 10% povidone-iodine or aqueous 4% chlorhexidine gluconate can be selected for skin antisepsis on the basis of solution availability, patient contraindications, or product cost. These findings might also have implications for antisepsis of other traumatic wounds.

FUNDING

US Department of Defense, Canadian Institutes of Health Research, McMaster University Surgical Associates, PSI Foundation.

Calibrated Decoders for Experimental Quantum Error Correction

Arbitrarily long quantum computations require quantum memories that can be repeatedly measured without being corrupted. Here, we preserve the state of a quantum memory, notably with the additional use of flagged error events. All error events were extracted using fast, midcircuit measurements and resets of the physical qubits. Among the error decoders we considered, we introduce a perfect matching decoder that was calibrated from measurements containing up to size-four correlated events. To compare the decoders, we used a partial postselection scheme shown to retain ten times more data than full postselection. We observed logical errors per round of 2.2±0.1×10^{-2} (decoded without postselection) and 5.1±0.7×10^{-4} (full postselection), which was less than the physical measurement error of 7×10^{-3} and therefore surpasses a pseudothreshold for repeated logical measurements.

Association of COVID-19 With Achieving Time-to-Surgery Benchmarks in Patients With Musculoskeletal Trauma

Question

Were resource constraints due to the COVID-19 pandemic associated with a delay in urgent fracture surgery beyond national time-to-surgery benchmarks?

Findings

In this cohort pre-post study that included 3589 patients, there was no association between time to surgery and COVID-19 in either open fracture or closed femur/hip fracture cohorts.

Meaning

Despite concerns that the unprecedented challenges associated with the COVID-19 pandemic would delay acute management of urgent surgery, many hospital systems within the US were able to implement strategies in keeping with time-to-surgery standards for orthopedic trauma.

Importance

In response to the COVID-19 pandemic, many hospital systems were forced to reduce operating room capacity and reallocate resources. The outcomes of these policies on the care of injured patients and the maintenance of emergency services have not been adequately reported.

Objective

To evaluate whether the COVID-19 pandemic was associated with delays in urgent fracture surgery beyond national time-to-surgery benchmarks.

Design, Setting, and Participants

This retrospective cohort study used data collected in the Program of Randomized Trials to Evaluate Preoperative Antiseptic Skin Solutions in Orthopaedic Trauma among at 20 sites throughout the US and Canada and included patients who sustained open fractures or closed femur or hip fractures.

Exposure

COVID-19–era operating room restrictions were compared with pre–COVID-19 data.

Main Outcomes and Measures

Surgery within 24 hours after injury.

Results

A total of 3589 patients (mean [SD] age, 55 [25.4] years; 1913 [53.3%] male) were included in this study, 2175 pre–COVID-19 and 1414 during COVID-19. A total of 54 patients (3.1%) in the open fracture cohort and 407 patients (21.8%) in the closed hip/femur fracture cohort did not meet 24-hour time-to-surgery benchmarks. We were unable to detect any association between time to operating room and COVID-19 era in either open fracture (odds ratio [OR], 1.40; 95% CI, 0.77-2.55; P = .28) or closed femur/hip fracture (OR, 1.01; 95% CI, 0.74-1.37; P = .97) cohorts. In the closed femur/hip fracture cohort, there was no association between time to operating room and regional COVID-19 prevalence (OR, 1.07; 95% CI, 0.70-1.64; P = .76).

Conclusions and Relevance

In this cohort study, there was no association between meeting time-to-surgery benchmarks in either open fracture or closed femur/hip fracture during the COVID-19 pandemic compared with before the pandemic. This is counter to concerns that the unprecedented challenges associated with managing the COVID-19 pandemic would be associated with clinically significant delays in acute management of urgent surgical cases and suggests that many hospital systems within the US were able to effectively implement policies consistent with time-to-surgery standards for orthopedic trauma in the context of COVID-19–related resource constraints.

Abstract P2-03-09: An institutional look back: Maximizing the utility of MammaPrint® in invasive breast cancer diagnostics without breaking the bank

Background: Subtyping of invasive breast cancer utilizing immunohistochemical stains for estrogen receptor, progesterone receptor, and HER2, with or without the proliferation marker Ki-67, is the current standard of care employed by pathologists. The development of the BluePrint® molecular subtyping assay by Agendia, a microarray-based gene expression test used in conjunction with MammaPrint, to molecularly subtype and assess recurrence risk in early-stage breast cancer, has breast surgeons and oncologists challenging the status quo.

Study Objectives: With increasing emphasis placed of proper use of declining resources, the current study aimed to determine parameters in which such testing has the greatest added value.

Materials and Methods: All invasive breast cancer biopsies and resection specimens with formalin fixed paraffin embedded tissue sent for testing at Agendia Genomics Laboratory from April 2015 to May 2017 were reviewed in an institutional look back. 87 cases were reviewed and conventional immunohistochemical cancer profiling, tumor size, and grade were compared with MammaPrint prognostic reports.

Results and Discussion: Of the 87 cases compared, 67 (77%) showed concordance between immunohistochemical and molecular subtyping. Of the 20 discordant cases, 13 (65%) were subtyped as low risk luminal A by Mammaprint/BluePrint despite demonstrating high risk clinicopathologic features including larger size (average 2 cm vs overall average 1.4 cm), higher grade (1 low grade, 11 intermediate grade, and 1 high grade vs totals of 36 low grade, 42 intermediate grade, and 20 high grade), and increased proliferation indices. 3 (15%) of discordant cases revealed HER2 amplification by fluorescence in situ hybridization. Near complete agreement was found among basal subtype and Luminal A tumors with Ki-67 less than 12%, indicating the lack of added value among these cases.

Conclusion: Study results validate the limited role of MammaPrint/BluePrint in cases of invasive breast cancer. Specifically, the greatest value of MammaPrint/BluePrint was recognized in luminal subtypes with intermediate grade and proliferation indices ranging from 12 – 29%.

Citation Format: Cross AW, McEvoy JR. An institutional look back: Maximizing the utility of MammaPrint® in invasive breast cancer diagnostics without breaking the bank [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-03-09.

Experimental Demonstration of Fault-Tolerant State Preparation with Superconducting Qubits

Robust quantum computation requires encoding delicate quantum information into degrees of freedom that are hard for the environment to change. Quantum encodings have been demonstrated in many physical systems by observing and correcting storage errors, but applications require not just storing information; we must accurately compute even with faulty operations. The theory of fault-tolerant quantum computing illuminates a way forward by providing a foundation and collection of techniques for limiting the spread of errors. Here we implement one of the smallest quantum codes in a five-qubit superconducting transmon device and demonstrate fault-tolerant state preparation. We characterize the resulting code words through quantum process tomography and study the free evolution of the logical observables. Our results are consistent with fault-tolerant state preparation in a protected qubit subspace.

Broadband Amplification of Low-Terahertz Signals Using Axis-Encircling Electrons in a Helically Corrugated Interaction Region

Experimental results are presented of a broadband, high power, gyrotron traveling wave amplifier (gyro-TWA) operating in the (75-110)-GHz frequency band and based on a helically corrugated interaction region. The second harmonic cyclotron mode of a 55-keV, 1.5-A, axis-encircling electron beam is used to resonantly interact with a traveling TE_{21}-like eigenwave achieving broadband amplification. The gyro-TWA demonstrates a 3-dB gain bandwidth of at least 5.5 GHz in the experimental measurement with 9 GHz predicted for a wideband drive source with a measured unsaturated output power of 3.4 kW and gain of 36-38 dB. The approach may allow a gyro-TWA to operate at 1 THz.

Experimental Demonstration of a Resonator-Induced Phase Gate in a Multiqubit Circuit-QED System

The resonator-induced phase (RIP) gate is an all-microwave multiqubit entangling gate that allows a high degree of flexibility in qubit frequencies, making it attractive for quantum operations in large-scale architectures. We experimentally realize the RIP gate with four superconducting qubits in a three-dimensional circuit-QED architecture, demonstrating high-fidelity controlled-z (cz) gates between all possible pairs of qubits from two different 4-qubit devices in pair subspaces. These qubits are arranged within a wide range of frequency detunings, up to as large as 1.8 GHz. We further show a dynamical multiqubit refocusing scheme in order to isolate out 2-qubit interactions, and combine them to generate a 4-qubit Greenberger-Horne-Zeilinger state.

Generation of electromagnetic fields of extremely high intensity by coherent summation of Cherenkov superradiance pulses

We demonstrate both theoretically and experimentally the possibility of correlating the phase of a Cherenkov superradiance (SR) pulse to the sharp edge of a current pulse, when spontaneous emission of the electron bunch edge serves as the seed for SR processes. By division of the driving voltage pulse across several parallel channels equipped with independent cathodes we can synchronize several SR sources to arrange a two-dimensional array. In the experiments carried out, coherent summation of radiation from four independent 8-mm wavelength band SR generators with peak power 600 MW results in the interference maximum of the directional diagram with an intensity that is equivalent to radiation from a single source with a power of 10 GW.

Demonstration of a quantum error detection code using a square lattice of four superconducting qubits

The ability to detect and deal with errors when manipulating quantum systems is a fundamental requirement for fault-tolerant quantum computing. Unlike classical bits that are subject to only digital bit-flip errors, quantum bits are susceptible to a much larger spectrum of errors, for which any complete quantum error-correcting code must account. Whilst classical bit-flip detection can be realized via a linear array of qubits, a general fault-tolerant quantum error-correcting code requires extending into a higher-dimensional lattice. Here we present a quantum error detection protocol on a two-by-two planar lattice of superconducting qubits. The protocol detects an arbitrary quantum error on an encoded two-qubit entangled state via quantum non-demolition parity measurements on another pair of error syndrome qubits. This result represents a building block towards larger lattices amenable to fault-tolerant quantum error correction architectures such as the surface code.

The physical realization of a quantum computer requires built-in error-correcting codes that compensate the disruption of quantum information arising from noise. Here, the authors demonstrate a quantum error detection scheme for arbitrary single-qubit errors on a four superconducting qubit lattice.

High power wideband gyrotron backward wave oscillator operating towards the terahertz region

Experimental results are presented of the first successful gyrotron backward wave oscillator (gyro-BWO) with continuous frequency tuning near the low-terahertz region. A helically corrugated interaction region was used to allow efficient interaction over a wide frequency band at the second harmonic of the electron cyclotron frequency without parasitic output. The gyro-BWO generated a maximum output power of 12 kW when driven by a 40 kV, 1.5 A, annular-shaped large-orbit electron beam and achieved a frequency tuning band of 88-102.5 GHz by adjusting the cavity magnetic field. The performance of the gyro-BWO is consistent with 3D particle-in-cell numerical simulations.

Flexor tendon injuries following locked volar plating of distal radius fractures

We present 2 cases showing that flexor pollicis longus and flexor digitorum profundus index injury can occur after placement of 2 commonly used locked volar plates. In contrast with the literature, the radii healed in an anatomic position without plate lift-off. The patients presented 6 and 8 months after surgery with new onset of radial wrist pain and tenderness at the site of the plate and absence or weakness of the flexor pollicis longus. In both cases, the plate was positioned anterior to the distal radial rim on the lateral radiograph. We suggest close follow-up of all fractures in which the distal end of the plate is anterior to the radial rim and removal of hardware if symptoms suggest tendon irritation.

Experimental and theoretical studies of a coaxial free-electron maser based on two-dimensional distributed feedback

The first operation of a coaxial free-electron maser (FEM) based on two-dimensional (2D) distributed feedback has been recently observed. Analytical and numerical modeling, as well as measurements, of microwave radiation generated by a FEM with a cavity defined by coaxial structures with a 2D periodic perturbation on the inner surfaces of the outer conductor were carried out. The two-mirror cavity was formed with two 2D periodic structures separated by a central smooth section of coaxial waveguide. The FEM was driven by a large diameter (7 cm), high-current (500 A), annular electron beam with electron energy of 475 keV. Studies of the FEM operation have been conducted. It has been demonstrated that by tuning the amplitude of the undulator or guide magnetic field, modes associated with the different band gaps of the 2D structures were excited. The Ka-band FEM generated 15 MW of radiation with a 6% conversion efficiency, in good agreement with theory.

Subsystem fault tolerance with the Bacon-Shor code

We discuss how the presence of gauge subsystems in the Bacon-Shor code [D. Bacon, Phys. Rev. A 73, 012340 (2006)10.1103/PhysRevA.73.012340 (2006)] leads to remarkably simple and efficient methods for fault-tolerant error correction (FTEC). Most notably, FTEC does not require entangled ancillary states, and it can be implemented with nearest-neighbor two-qubit measurements. By using these methods, we prove a lower bound on the quantum accuracy threshold, 1.94 x 10(-4) for adversarial stochastic noise, that improves previous lower bounds by nearly an order of magnitude.

Experimental study of coaxial free-electron maser based on two-dimensional distributed feedback

The first experimental study of a coaxial free-electron maser (FEM) based on two-dimensional (2D) distributed feedback is presented. A new type of cavity formed with coaxial 2D surface photonic band gap structures was used. The FEM was driven by a large diameter (7 cm), high-current (500 A), annular electron beam of energy 475 keV. By tuning the amplitude of the undulator or guide magnetic field, modes associated with the different band gaps of the 2D structures were excited. The -band coaxial FEM generated 15 MW of radiation with a 6% conversion efficiency, in excellent agreement with theory.

Dispersion of helically corrugated waveguides: analytical, numerical, and experimental study

Helically corrugated waveguides have recently been studied for use in various applications such as interaction regions in gyrotron traveling-wave tubes and gyrotron backward-wave oscillators and as a dispersive medium for passive microwave pulse compression. The paper presents a summary of various methods that can be used for analysis of the wave dispersion of such waveguides. The results obtained from an analytical approach, simulations with the three-dimensional numerical code MAGIC, and cold microwave measurements are analyzed and compared.

Compression of frequency-modulated pulses using helically corrugated waveguides and its potential for generating multigigawatt rf radiation

A new method to generate ultrahigh-power microwave pulses compatible with mildly relativistic electron sources is proposed. This method involves a novel microwave compressor in the form of a metal helically corrugated waveguide, which can enhance the power of frequency-modulated nanosecond pulses up to the multigigawatt level. The results of the proof-of-principle experiments at kilowatt power levels are in good agreement with theory.

Experimental studies of the influence of distributed power losses on the transparency of two-dimensional surface photonic band-gap structures

Two-dimensional (2D) surface photonic band-gap (SPBG) structures have been suggested to realize 2D distributed feedback. The 2D SPBG structures can be obtained by providing 2D periodic perturbations of the waveguide surface. Such a structure can be used in a wide variety of applications including microwave electronics and integrated optics. The theoretically predicted effect of the transparency of the 2D SPBG structure when distributed Ohmic losses inside the structure are relatively high in comparison with the wave coupling coefficient has been observed in a series of experiments. The results obtained are in good agreement with theoretical predictions.

Social support and psychological functioning among high-risk mothers: the impact of the Baby Love Maternal Outreach Worker Program

This study compared two groups of high-risk Medicaid-eligible mothers, 221 who participated in a maternal home visitation program and 198 who did not, to determine whether program participation was associated with improvements in the mothers' psychological functioning 1 year after delivery, and whether these improvements were associated with the type and intensity of support provided by home visitors. The results suggest that, compared to nonparticipants, participants provided with more intensive home visitor support had significantly higher self-esteem (p = 0.039) and were less depressed (p = 0.015). Participants with less intensive home visitor support, however, did not differ significantly from nonparticipants in their self-esteem or depression levels. No significant differences were observed in the perceived stress levels of participants as compared with nonparticipants, regardless of the intensity of home visitor support. Mothers who had support from the baby's father, however, had significantly lower perceived stress levels than mothers with no support from the baby's father (p = 0.046). Moreover, the type of support provided by home visitors (emotional, instrumental, informational) did not appear to be related to the mothers' psychological functioning. This study suggests that the intensity of support is an important component of maternal home visitation programs that aim to improve women's psychological functioning.

High-gain wide-band gyrotron traveling wave amplifier with a helically corrugated waveguide

First bandwidth measurements of a novel gyrotron amplifier are presented. The coupling between the second harmonic cyclotron mode of a gyrating electron beam and the radiation field occurred in the region of near infinite phase velocity over a broad bandwidth by using a cylindrical waveguide with a helical corrugation on its internal surface. With a beam energy of 185 keV, the amplifier achieved a maximum output power of 1.1 MW, saturated gain of 37 dB, linear gain of 47 dB, saturated bandwidth of 8.4 to 10.4 GHz ( 21% relative bandwidth), and an efficiency of 29%, in good agreement with theory.

Self-amplification of coherent spontaneous emission in a cherenkov free-electron maser

Ultrashort pulses of microwave radiation have been produced in a dielectric-lined Cherenkov free-electron maser (FEM) amplifier. An intense initial seed pulse, due to coherent spontaneous emission (CSE), arises at the leading edge of the electron pulse. There is evidence to show that 3-4 cycle spikes are produced through the amplification of these seed pulses. A strong dependence of the start-up power on the rise time of the electron pulse has been found. The experimental results are verified by a theoretical analysis. Our study shows that amplification in a FEM amplifier is always initiated by CSE arising from the edge of the electron pulse when the rise time is comparable to the electromagnetic wave period.

Factors predicting completion of a home visitation program by high-risk pregnant women: the North Carolina Maternal Outreach Worker Program

OBJECTIVES

This study sought to identify characteristics of high-risk pregnant women that predicted long-term participation in a home visitation program.

METHODS

Data regarding sociodemographic characteristics, perceived needs, psychological functioning, substance use, and informal social support were collected prospectively from 152 short-term and 221 long-term program participants.

RESULTS

In comparison with short-term participants, long-term participants were more likely to have been African American, married, nonsmokers, and enrolled in the program during their second trimester of pregnancy, and they were more likely to have had emotional and instrumental support needs.

CONCLUSIONS

Women with greater social support needs and healthier behaviors were more receptive to long-term home visitation than other women.

Generation of powerful subnanosecond microwave pulses by intense electron bunches moving in a periodic backward wave structure in the superradiative regime

Experimental results of the observation of coherent stimulated radiation from subnanosecond electron bunches moving through a periodic waveguide and interacting with a backward propagating wave are presented. The subnanosecond microwave pulses in Ka and W bands were generated with repetition frequencies of up to 25 Hz. The mechanism of microwave pulse generation was associated with self-bunching, and the mutual influence of different parts of the electron pulse due to slippage of the wave with respect to the electrons; this can be interpreted as superradiance. The illumination of a panel of neon bulbs resulted in a finely structured pattern corresponding to the excitation of the TM01 mode. Observation of rf breakdown of ambient air, as well as direct measurements by hot-carrier germanium detectors, leads to an estimate of the absolute peak power as high as 60 MW for the 300-ps pulses at 38 GHz. These results are compared with numerical simulations. The initial observation of 75-GHz, 10-15-MW radiation pulses with a duration of less than 150 ps is also reported.

Theory and design of a free-electron maser with two-dimensional feedback driven by a sheet electron beam

The use of two-dimensional Bragg resonators of planar geometry, realizing two-dimensional (2D) distributed feedback, is considered as a method of producing spatially coherent radiation from a large sheet electron beam. The spectrum of eigenmodes is found for a 2D Bragg resonator when the sides of the resonator are open and also when they are closed. The higher selectivity of the open resonator in comparison with the closed one is shown. A time-domain analysis of the excitation of an open 2D Bragg resonator by a sheet electron beam demonstrates that a single-mode steady-state oscillation regime may be obtained for a sheet electron beam of width 100-1000 wavelengths. Nevertheless, for a free-electron maser (FEM) with a closed 2D Bragg resonator, a steady-state regime can also be realized if the beam width does not exceed 50-100 wavelengths. The parameters for a FEM with a 2D planar Bragg resonator driven by a sheet electron beam based on the U-2 accelerator (INP RAS, Novosibirsk) are estimated and the project is described.

State health department and university evaluation of North Carolina's Maternal Outreach Worker Program

INTRODUCTION

The Maternal Outreach Worker (MOW) Program is a social support intervention using lay helpers to provide support, health education, and outreach to Medicaid eligible women at risk for poor pregnancy and parenting outcomes. State Health Department and University collaborators designed a two-pronged evaluation comprised of programwide and interview study components to assess the impact of the program on pregnancy outcomes, health behaviors, and infant health status.

METHODS

Programwide evaluation data are based on 1992-1995 N.C. birth files for the original 24 participating counties and include 1,726 MOW participant births and 12,988 comparison births whose records were linked to birth files and met the study criteria. For the interview study 373 MOW participants and 332 comparison women were personally interviewed three times: during pregnancy, one month postpartum, and one year after delivery.

RESULTS

Risk factors associated with poor pregnancy and parenting outcomes were greater among MOW participants than comparisons in both the programwide and intensive study components. Caucasian MOW participants had slightly higher rates of adequate prenatal care. African Americans were found to have less adequate prenatal care. Fewer than expected LBW and VLBW births were observed for African-American MOW participants. MOW Program participation did not affect the utilization of health and social services for infants. African Americans, regardless of whether they received MOW services, fared better than Caucasians in terms of having their pregnancy needs fulfilled.

CONCLUSIONS

Findings show the need to further explore appropriate measures of maternity support program outcomes and indicate inconsistent program benefit among subpopulations.

Health outcomes of children receiving EPSDT checkups: a pilot study

This pilot study used medical records to examine the health outcomes of children receiving care in Medicaid's Early and Periodic Screening, Diagnosis and Treatment (EPSDT) program. Medical records from 76 children seen for EPSDT visits during a 6-month period were reviewed to assess whether health problems were identified and whether treatment, follow-up, or referral care was provided. Health problems were identified for 43% of the children; 22% received treatment, and 18% were referred for specialty care. Checkups uncovered fewer problems than would be expected in a poor, largely minority population. Almost one third of the children referred for specialty care apparently did not receive such care. The study verified the need for further research and provides direction for future study.

Comprehensiveness of well child checkups for children receiving Medicaid: a pilot study

Early and Periodic Screening, Diagnosis, and Treatment (EPSDT) is a Medicaid program designed to provide comprehensive well child care for children from low-income families. Each EPSDT checkup should include a physical examination; medical history; assessment of development, nutrition, and immunizations; assessment of hearing, vision, and dental status; and anticipatory guidance. This pilot study of the medical records of 76 children receiving EPSDT checkups in six rural counties in North Carolina provided a preliminary assessment of whether EPSDT checkups included the required components. The study showed that health care providers frequently did not provide adequate documentation of the care provided at the checkup, and it raised questions as to whether children received the required components of the EPSDT checkup.

Demographic and health characteristics of participants and nonparticipants in a work site health-promotion program

Work site health-promotion programs represent an increasingly common attempt by industry to improve the health of employees. The potential impact of programs is limited by nonparticipation, especially among demographic subgroups and those who could most benefit from health behavior change. The present study prospectively examined the relationship of personnel data and self-reported health habits and health status to participation in the health-promotion program at a research and development work site. Thirty-four percent of the 505 employees enrolled in the health-promotion program. White employees were 2.47 times as likely to participate as nonwhites (95% confidence interval, 1.59, 3.83). Those with health maintenance organization health insurance were 1.43 times as likely to participate as were employees with fee-for-service insurance (1.11, 1.84). There was no difference between participants and nonparticipants in self-reported health status, and only slightly more positive health habits were noted among participants. Seatbelt use was 1.65 times more common among participants (1.10, 2.49). The study results are reassuring that such programs do not enroll only the very healthy or those with healthy habits. However, the diminished enrollment of nonwhite employees supports concern that health-related programs may not equally reach all segments of the work force.

Psychosocial predictors of participation in a work site health-promotion program

An understanding of psychosocial factors associated with participation in health promotion programs could lead to targetted interventions to increase enrollment. This study used questionnaires to measure employees' perception of program efficacy, health attitudes, beliefs, social support, and stress prior to the introduction of a comprehensive health promotion program at a research and development work site. The association of these factors with enrollment in the program was then prospectively determined. In addition, open-ended questionnaires were used retrospectively to determine additional factors associated with participation. Of the above factors, only program efficacy was significantly associated with participation in the entire sample. Perceived social support was associated with participation among non-white employees. In open-ended questionnaires, a desire for health information, a desire for help with behavior change, and concern about health status were the most commonly given reasons for participating. The study findings imply that environmental factors operating during the enrollment period at the work site may be more powerful than preexisting attitudes and beliefs in determining participation.

Infant mortality: a practical approach to the analysis of the leading causes of death and risk factors

The analysis of infant mortality data provides an opportunity for developing preventive strategies to improve this indicator of a population's health. All infant deaths in North Carolina during a 5-year period (1980 through 1984) were analyzed using the International Classification of Diseases, 9th revision (ICD-9), and a system for linked birth and death records that allows the analysis of birth certificate information on deaths. Causes of death were aggregated based on common etiology such as prematurity or obstetric-related conditions rather than the more traditional organ system taxonomy of the ICD-9 codes. Analyses were carried out separately for very low birth weight (less than or equal to 1500 g), moderately low birth weight (1501 through 2500 g), and normal birth weight (greater than 2500 g) babies. Maternal characteristics identified from the birth certificate were also compared with the different causes of death. Prematurity-related conditions accounted for 37.5% of all deaths, ranking far above the 17.4% for congenital anomalies and 12.9% for sudden infant death syndrome. For normal birth weight babies, sudden infant death syndrome ranked first, followed by congenital anomalies and nonperinatal infections. For the moderately low birth weight babies, congenital anomalies ranked first, with sudden infant death syndrome second and prematurity-related conditions third. For the very low birth weight babies, prematurity-related conditions accounted for nearly 70% of the deaths, with obstetric conditions and congenital anomalies ranking second and third, respectively. Maternal risk factors identified an overrepresentation of nonwhite, unmarried, and young teenage mothers and mothers with less than adequate prenatal care.(ABSTRACT TRUNCATED AT 250 WORDS)

Preschool risk factors as predictors of early school performance

The relative importance of selected developmental, medical, and social factors in assessing a child's early academic potential was evaluated prospectively in a rural southern school district. Two hundred and ten (210) preschoolers were given the Sprigle School Readiness Screening Test (SSRST) and the Beery Test of Visual Motor Integration (VMI) while physicians rated the children's attention span. A parental questionnaire assessed medical, behavioral, social, and family variables. Follow-up school data were available on 176 children (84%). Using regression techniques, reading and math achievement scores were directly correlated with maternal education, SSRST and VMI results, and lack of family history of learning problems, whereas grade failure was associated with low VMI scores, decreased maternal education, boys with late birthdays, and family history of learning problems. Medical problems and parental preschool behavior concerns were unrelated to school achievement, but physician rating of preschool attention span showed a significant correlation with reading and math scores. A 0-11 Risk Index of School Capability (RISC) scale based on data analyses was developed to rate a preschooler's early academic potential. A score of 7 or above had a 98% positive predictive value of successful grade completion, whereas a score of 3 or below had a 70% predictive value for grade failure. The value of assessing the scores of the VMI and SSRST alone was also considered, but was found less useful. This study demonstrates the importance of evaluating a number of risk factors in assessing a preschooler's early academic potential. Such data can be used to focus school resources for children at increased risk for grade failure.

Comparisons between inner-city and private school adolescents' perceptions of health problems

A youth health survey was administered to 247 students in an inner-city ghetto high school and 404 students in a private boarding school. Significant differences between the two socioeconomic groups were found for responses about health information, health concerns and problems, and health status and service utilization. Sex-related issues were of greater concern to the private school youth and they desired more help with depression-sadness and birth control. Inner-city youth had more health worries and indicated a desire for more help with physical problems such as toothaches, headaches, and stomach aches, and social problems such as racial discrimination and parent relations. From a list of 22 health problems, the inner-city youth ranked dental problems, acne, and health worries highest while the private school youth ranked depression-sadness, tiredness, and acne highest. Regardless of social class, most adolescents perceived large gaps in their health education. One implication of our data is that the specific self-reported needs and concerns of adolescents should be considered in planning health services and education programs.

Ethical and cultural dimensions of informed consent. A case study and analysis

A case of a patient with angina who was considered for coronary bypass surgery illustrates the issue of informed consent. Ethical and legal aspects and the inherent limitations of achieving consent must be considered. Physicians may have personal biases, which may lead to coerced consent, or may overwhelm the patient with information on potential complications of a proposed procedure, which may lead to consent without hope. Patient bias or misinformation may lead to misunderstood consent or, if the patient's judgment is distorted, to crisis consent. The patient's desire to defer the decision to the physician raises the question of whether such requested paternalism violates patient self-determination and invalidates consent or is an exercise of the patient's right to have his physician decide. The case presented exemplifies the patient-physician interaction needed for responsible paternalism.