Classical capacity of the lossy bosonic channel: the exact solution.

The classical capacity of the lossy bosonic channel is calculated exactly. It is shown that its Holevo information is not superadditive, and that a coherent-state encoding achieves capacity. The capacity of far-field, free-space optical communications is given as an example.

Long distance, unconditional teleportation of atomic states via complete Bell state measurements.

We propose a scheme for creating and storing quantum entanglement over long distances. Optical cavities that store this long-distance entanglement in atoms could then function as nodes of a quantum network, in which quantum information is teleported from cavity to cavity. The teleportation is conducted unconditionally via measurements of all four Bell states, using a novel method of sequential elimination.

Anesthesia by the pediatric specialist.

There is increasing evidence that involvement of pediatric anesthesiologists in the perioperative care of infants and children can positively impact outcome. Considerable data have emerged in the past several years that clearly show that infants and small children experience untoward events at a much higher rate than do older children and adults. Herein the author presents some of this literature as well as data suggesting that anesthesiologists with interest and additional training in the care of infants and children can improve anesthesia outcomes. Even in these days of cost containment, it makes sense to provide the best pediatric team to care for the pediatric patient during the perioperative experience.

Raising eyebrows: problems that get anesthesiologists' attention.

There are many clinical situations of concern that may be unique to pediatric anesthesiologists. The author discusses four of the more common presentations: asthma, cystic fibrosis, anterior mediastinal masses, and latex allergy. Many such issues can be resolved before surgery by consultation with members of the operating team. Some issues may require additional input from nonsurgical pediatric specialists. By maintaining good communication between the anesthesiologist and the surgeon, delays and cancellations can be minimized and patient care enhanced.

Maximum-likelihood multiresolution laser radar range imaging.

Maximum-likelihood range imaging is considered for pulsed-imager operation of a coherent laser radar. The expectation-maximization (EM) algorithm is used to develop an explicit procedure for maximum-likelihood fitting of a multiresolution (wavelet) basis-at a sequence of increasingly fine resolutions-to laser radar range data. Specialization to the Haar-wavelet basis yields a procedure that is both computationally efficient and numerically robust. Basic analytical properties of the estimation algorithm and its performance are presented, along with results based on simulated and real laser radar range data. It is shown that the weights associated with the expectation-maximization iterations provide a reliable indicator for terminating the coarse-to-fine resolution progression. At the weight-determined stopping point, estimation performance approaches the ultimate limit set by the complete-data bound.

Raman-noise limit on squeezing in continuous-wave four-wave mixing.

The continuous-time quantum theory of self-phase modulation (SPM) in lossless, dispersionless, single-mode fiber requires a nonzero response time, to capture the classical SPM limit properly, and an accompanying Raman noise, to ensure commutator preservation. The continuous-wave, four-wave mixing limit of this theory is shown to harbor a Raman-noise limit on fiber-based squeezed-state generation.

Methemoglobin levels during prolonged combined nitroglycerin and sodium nitroprusside infusions in infants after cardiac surgery.

Nitroglycerin (NTG) and sodium nitroprusside (SNP) are routinely used perioperatively in infants with congenital heart defects. In this study, NTG and SNP were infused in the operating room to increase venous capacitance, reduce systemic and pulmonary afterload, facilitate weaning off cardiopulmonary bypass, stabilize hemodynamics for transport to the intensive care unit (ICU), and reduce the fluid resuscitation needed upon arrival in the ICU. Because of the risk for accumulation of methemoglobin (MetHb) and cyanmethemoglobin (cyan-MetHb) during prolonged continuous infusion of NTG and SNP, it was decided to (1) quantify ICU use, (2) measure % MetHb at 12-hour intervals, and (3) look indirectly for the accumulation of cyan-MetHb by comparing simultaneous pulse oximetry (SpO2) (Nellcor N-100 [Nellcor, Haywood, CO]) and CO-oximetry (SaO2) (Corning 270 [Corning, Medfield, MA]). A total of 69 arterial samples were obtained from 16 infants (median age 4.4 months) following cardiac surgery with bypass. Median doses of NTG, 6.0 mg/kg (range 0.7 to 27.5), and SNP, 3.3 mg/kg (range 0.6 to 33.4), were infused over a median of 64.5 hours (range 12 to 183) (N = 16 patients). The median MetHb was 0.6% (range 0.0 to 1.5) after infusions of NTG, 1.8 micrograms/kg/min (range 0.5 to 4), and SNP, 1.3 micrograms/kg/min (range 0.3 to 8.4) (N = 69 measurements). Regression analysis of oximetry data yielded the equation: SpO2 = 1.04 SaO2 - 3.7%, r = 0.97. The mean difference between SpO2 and SaO2 data pairs was 0.0% (bias) with a SD (precision) of +/- 2.3%.(ABSTRACT TRUNCATED AT 250 WORDS)

Bradycardia during anesthesia in infants. An epidemiologic study.

BACKGROUND: The frequency and morbidity of bradycardia during anesthesia in infants are not well documented. This study sought to determine the frequency of bradycardia during anesthesia in infants (0 to 1 yr) compared to that in older children, describe causes and morbidity, and identify factors that influence its frequency. METHODS: Computerized information abstracted from 7,979 anesthetic records of patients ages 0-4 yr undergoing noncardiac surgery were examined for the presence or absence of intraoperative bradycardia. To study bradycardia in infants, 4,645 anesthetics in patients aged 0-1 yr were considered. Those with bradycardia to heart rates less than 100 beats/min were examined for causes, morbidity, and treatment of the bradycardia. For analysis of influencing factors, the frequency of bradycardia in infants was related to age, sex, race, ASA physical status, surgical site (body cavity), complexity (major or minor) and duration, type of primary anesthetist, type of supervising anesthesiologist, and anesthetic agents. Logistic regression was used to estimate the significance (P < 0.05) and odds ratios for each. RESULTS: The frequency of bradycardia was 1.27% in the 1st yr of life, but only 0.65% in the third and 0.16% in the 4th yr, a significant difference. Causes of bradycardia in infants included disease or surgery in 35%, the dose of inhalation agent in 35%, and hypoxemia in 22%. Morbidity included hypotension in 30%, asystole or ventricular fibrillation in 10%, and death in 8%. Treatment involved epinephrine in 30% and chest compression in 25%. Associated factors included an ASA physical status of 3-5 (vs. 1 or 2) and longer (vs. shorter) surgery. Bradycardia was less than half as likely when the supervising anesthesiologist was a member of the Pediatric Anesthesia Service as with other anesthesiologists (P < 0.001). CONCLUSIONS: Bradycardia is more frequent in infants undergoing anesthesia compared to older children and is associated with substantial morbidity. It is more likely in sicker infants undergoing prolonged surgery and less likely when a pediatric anesthesiologist is present.

Dr Henry Garland: the man, the myth, the legend, and the legacy. Garland Lecture from the 1991 California Radiological Society meeting.

In a century of American radiology, a relatively small number of radiologists have emerged as unquestioned leaders of the specialty. One of those was L. Henry Garland, late of San Francisco, whose multifaceted accomplishments and vigorous personality made him a significant contributor to advances in radiology during 3 decades. The Garland family has endowed an annual lecture at the meeting of the California Radiological Society. This essay is taken from the 1991 lecture, which was an assessment of Garland's significance.

Frequency of anesthetic cardiac arrests in infants: effect of pediatric anesthesiologists.

STUDY OBJECTIVE: To determine whether the presence of pediatric anesthesiologists decreases the frequency of anesthetic-related cardiac arrests in infants (children who are 1 year of age or younger). DESIGN: A comparative retrospective study of anesthetics and cardiac arrests during a 7-year period. SETTING: The main operating room (OR) suite of a large university hospital. PATIENTS: All patients age 1 year or less undergoing surgical anesthesia from July 1983 through March 1990. INTERVENTIONS: Computerized anesthetic and operative patients records were queried for patient age, ASA physical status, body weight, surgical procedure, intraoperative complications, and the identity of the attending anesthesiologist. In each case, it was determined whether a pediatric anesthesiologist was in attendance and whether a cardiac arrest due to anesthesia occurred. Pediatric anesthesiologists were identified as those with pediatric fellowship training or the equivalent. The study population was divided into two groups: (1) the pediatric anesthesiologist group, with 2,310 patients whose anesthetics were supervised by pediatric anesthesiologists; (2) the nonpediatric anesthesiologist group, with 2,033 patients. MEASUREMENTS AND MAIN RESULTS: Mean age and weight were comparable in the two groups, and the distribution of physical status did not differ. No anesthesia-related cardiac arrests occurred in the pediatric anesthesiologist group; four anesthetic cardiac arrests occurred in the nonpediatric anesthesiologist group, for a frequency of 19.7 per 10,000 anesthetics. This difference between provider groups is significant (Fisher's exact probability test, p = 0.048). CONCLUSIONS: The results suggest that the use of pediatric anesthesiologists for all infants 1 year of age or younger might decrease anesthetic morbidity in this age-group.

Single-beam squeezed-state generation in sodium vapor and its self-focusing limitations.

We describe an experiment that generates squeezed states by means of forward four-wave mixing in sodium vapor with a single optical beam. The single-beam arrangement maximizes the pump-probe spatial overlap in the nonlinear medium. Self-focusing (or self-defocusing) is found to be the major limiting factor in achieving optimal squeezing.

Quantum correlation and absorption spectroscopy in an optical parametric oscillator in the presence of pump noise.

We present a linearized quantum analysis of the optical parametric oscillator that includes the effects of pump noise. We show that excess pump noise reduces the intensity correlation between the signal and idler at low frequencies, which explains the low-frequency spectrum of current experimental observations. Its dependence on the cavity loss mismatch permits the possibility of ultrasensitive intracavity absorption spectroscopy, even in the absence of nonclassical correlation observation.

Nonclassical intensity correlation from a type I phase-matched optical parametric oscillator.

Signal and idler beams from a type I phase-matched nondegenerate optical parametric oscillator are separated by a Mach-Zehnder interferometer. Broadband nonclassical intensity correlation is observed, in agreement with a theory that includes pump noise. The maximum observed correlation, which occurs at 1.1 MHz, yields a noise level 2.8 dB below the shot noise.

Noise sources in laser radar systems.

To understand the fundamental limit of performance with a given laser radar system, the phase noise of a testbed laser radar has been investigated. Apart from the phase noise in the transmitter laser and the local oscillator laser, additional phase noise was introduced by vibrations caused by fans in power supplies and cooling systems. The stability of the mechanical structure of the platform was also found to be of great importance. Furthermore, a model for the signal variations from diffuse targets has been developed. This model takes into account the stray light, the speckle decorrelation, and Doppler shift due to moving targets.

Computed tomography of the normal and traumatized elbow.

To study the role of CT in the radiographic evaluation of the elbow, a technique was developed for producing axial scans of the elbow in flexed and extended positions. Computed tomography was performed on a total of 75 patients with acute or subacute elbow injuries. All scans were compared to their respective plain radiographs, and results correlated with each patient's clinical management. Based on these observations, six radiographic criteria were developed which, when present, should prompt further study of the elbow by CT. Under these six conditions, the information provided by CT may change the diagnosis and subsequent management of a patient's injuries.

Observation of squeezed noise produced by forward four-wave mixing in sodium vapor.

We have generated squeezed-state light through forward four-wave mixing in sodium vapor as verified by homodyne detection. Optical phase-sensitive noise with a minimum falling 4% below the shot-noise limit was observed.

Optical autodyne detection: theory and experiment.

Optical autodyne detection is a direct detection procedure for measuring relative Doppler frequency shifts using a laser transceiver. A theoretical study of the carrier-to-noise ratio and signal-to-noise ratio for an autodyne transceiver is presented. Experimental results, obtained with a cw autodyne transceiver, are reported. The relative merits of optical autodyne vs optical heterodyne detection are discussed.

Heterodyne mixing efficiency for detector arrays.

Monostatic radar equations are reported for laser-transceiver sensors that employ coherent optical detection over a linear-array photodetector. Explicit results are presented illustrating the impact of transmitter and receiver antenna patterns on the heterodyne mixing efficiency achieved by each detector element.