Optical spatial solitons at the interface between two dissimilar periodic media: theory and experiment.

Discrete spatial solitons traveling along the interface between two dissimilar one-dimensional arrays of waveguides were observed for the first time. Two interface solitons were found theoretically, each one with a peak in a different boundary channel. One evolves into a soliton from a linear mode at an array separation larger than a critical separation where-as the second soliton always exhibits a power threshold. These solitons exhibited different power thresholds which depended on the characteristics of the two lattices. For excitation of single channels near and at the boundary, the evolution behavior with propagation distance indicates that the solitons peaked near and at the interface experience an attractive potential on one side of the boundary, and a repulsive one on the opposite side. The power dependence of the solitons at variable distance from the boundary was found to be quite different on opposite sides of the interface and showed evidence for soliton switching between channels with increasing input power.

Sleep apnea and quality of life.

OBJECTIVE: To investigate the effects of sleep apnea (SA) on the quality of life (QOL). DESIGN: A prospective study of QOL in patients with and without SA as defined by an apnea-hypopnea index (AHI) >5. SETTING: University-based outpatient clinics. PATIENTS: Primary care patients followed in a general internal medicine clinic as well as those referred to a sleep disorders clinic at the University of Wisconsin Hospital and Clinics were consecutively recruited and classified into 3 groups of subjects: (1) patients without SA (AHI<5) (n=46), (2) patients with mild SA (AHI 5-15) (n=16), and (3) patients with moderate to severe SA (AHI>15) (n=21). INTERVENTIONS: NA. MEASUREMENTS: QOL was assessed with the Medical Outcomes Study SF-36 Health Survey. Health history and demographic data were obtained via structured interview and medical record review. All subjects underwent overnight polysomnography for diagnosis of SA. RESULTS: After controlling for age, gender, body mass index, and number of comorbid conditions, the association between sleep apnea and QOL was significant in the domains of physical functioning and role limitation due to physical health problems (p<0.05) and was borderline in vitality (p<0.1). Patients with both mild and moderately severe SA scored significantly lower (worse) than did patients without SA in physical functioning and in role limitations due to physical-health (82 and 83 vs. 92, respectively). Moderate to severe SA subjects scored significantly lower in vitality than did subjects without SA (51 vs. 64, p<0.05). Subscales analysis revealed that subjects with moderate to severe SA had significantly lower scores that did those without SA in positive affect (69 vs. 79), current health perceptions (71 vs. 80) and vitality (50 vs. 70), p<0.05 for all comparisons. A large percentage of patients without SA had perfect scores of 100 (ceiling effect) on the physical, social, and role functioning scales. CONCLUSIONS: SA has an independent impact on several QOL domains after adjusting for differences in age, gender, body mass index, and comorbidity. QOL outcomes were likely attenuated by ceiling effects. Disentangling the scales that measure multidimensional QOL (positive and negative aspects) enhanced the ability of the SF-36 to detect important consequences of sleep apnea on QOL.

Arithmetic coding with dual symbol sets and its performance analysis.

In this paper, we propose a novel adaptive arithmetic coding method that uses dual symbol sets: a primary symbol set that contains all the symbols that are likely to occur in the near future and a secondary symbol set that contains all other symbols. The simplest implementation of our method assumes that symbols that have appeared in the previously are highly likely to appear in the near future. It therefore fills the primary set with symbols that have occurred in the previously. Symbols move dynamically between the two symbol sets to adapt to the local statistics of the symbol source. The proposed method works well for sources, such as images, that are characterized by large alphabets and alphabet distributions that are skewed and highly nonstationary. We analyze the performance of the proposed method and compare it to other arithmetic coding methods, both theoretically and experimentally. We show experimentally that in certain contexts, e.g., with a wavelet-based image coding scheme that has appeared in the literature, the compression performance of the proposed method is better than that of the conventional arithmetic coding method and the zero-frequency escape arithmetic coding method.

Immediate improvement in coronary flow reserve after alcohol septal ablation in patients with hypertrophic obstructive cardiomyopathy.

OBJECTIVES: To examine whether percutaneous alcohol septal ablation affects coronary flow reserve (CFR) in patients with hypertrophic cardiomyopathy (HCM). METHODS: CFR was measured immediately before and after septal ablation in patients with symptomatic obstructive HCM. CFR was also obtained in normal subjects (NL) for comparison. RESULTS: Patients with HCM (n = 11), compared with NL (n = 22), had a lower mean (SD) baseline CFR (1.96 (0.5) vs 3.0 (0.7), p<0.001), a lower coronary resistance (1.04 (0.45) vs 3.0 (2.6), p = 0.002), a higher coronary diastolic/systolic velocity ratio (DSVR; 5.1 (3.0) vs 1.8 (0.5), p = 0.04) and a lower hyperaemic coronary flow per left ventricular (LV) mass (0.73 (0.4) vs 1.1 (0.6) ml/min/g, p = 0.007). Septal ablation in the HCM group (n = 7) reduced the outflow tract gradient but not the left atrial or LV diastolic pressures. Ablation resulted in immediate normalisation of CFR (to 3.1 (1), p = 0.01) and DSVR (to 1.9 (0.8), p = 0.09) and an increase in coronary resistance (to 1.91 (0.6), p = 0.02). This was probably related to an improvement in the systolic coronary flow. CONCLUSIONS: This study demonstrates that successful septal ablation in patients with symptomatic HCM results in immediate improvement in CFR, which is reduced in HCM partly because of the increased systolic contraction load.

Transcutaneous electrical acupoint-stimulation potentiates the anesthetic effect of enflurane in humans.

The effect of transcutaneous electrical acupoint stimulation (TEAS) on enflurane anesthesia and hemodynamic changes during craniotomy was studied. Eighty neurosurgical patients were randomly divided into two groups. Anesthesia was induced with fentanyl, droperidol, thiopental, and suxamethonium by intubation. In group A, anesthesia was maintained with enflurane (n=40), and in group B was supplemented by TEAS with Han's acupoint nerve stimulator (HANS) to Hegu, Yuyao, and Fengchi points on the operated side (n=40). The results showed that the ratio between expired concentration and minimum alveolar concentration of enflurane during operation in group B was 37.8%-47% lower than that in group A, and that the hemodynamics were more stable during operation. The results also demonstrated that the patients in Group B recovered faster after operation. It was concluded that TEAS with HANS significantly potentiated the anesthetic effect of enflurane.

Diagnosing syncope. Part 2: Unexplained syncope. Clinical Efficacy Assessment Project of the American College of Physicians.

PURPOSE: To review the literature on diagnostic testing in syncope that remains unexplained after initial clinical assessment. DATA SOURCES: MEDLINE search. STUDY SELECTION: Published papers were selected if they addressed diagnostic testing in syncope, near syncope, or dizziness. DATA EXTRACTION: Studies were identified as population studies, referral studies, or case series. DATA SYNTHESIS: After a thorough history, physical examination, and electrocardiography, the cause of syncope remains undiagnosed in 50% of patients. In such patients, information may be derived from the results of carefully selected diagnostic tests, especially 1) electrophysiologic studies in patients with organic heart disease, 2) Holter monitoring or telemetry in patients known to have or suspected of having heart disease, 3) loop monitoring in patients with frequent events and normal hearts, 4) psychiatric evaluation in patients with frequent events and no injury, and 5) tilt-table testing in patients who have infrequent events or in whom vasovagal syncope is suspected. Hospitalization is indicated for high-risk patients, especially those with known heart disease and elderly patients. CONCLUSIONS: A flexible, focused approach is required to diagnose syncope. Features of the initial history and physical examination help guide diagnostic testing.

Diagnosing syncope. Part 1: Value of history, physical examination, and electrocardiography. Clinical Efficacy Assessment Project of the American College of Physicians.

PURPOSE: To review the literature on diagnostic testing in syncope and provide recommendations for a comprehensive, cost-effective approach to establishing its cause. DATA SOURCES: Studies were identified through a MEDLINE search (1980 to present) and a manual review of bibliographies of identified articles. STUDY SELECTION: Papers were eligible if they addressed diagnostic testing in syncope or near syncope and reported results for at least 10 patients. DATA EXTRACTION: The usefulness of tests was assessed by calculating diagnostic yield: the number of patients with diagnostically positive test results divided by the number of patients tested or, in the case of monitoring studies, the sum of true-positive and true-negative test results divided by the number of patients tested. DATA SYNTHESIS: Despite the absence of a diagnostic gold standard and the paucity of data from randomized trials, several points emerge. First, history, physical examination, and electrocardiography are the core of the syncope workup (combined diagnostic yield, 50%). Second, neurologic testing is rarely helpful unless additional neurologic signs or symptoms are present (diagnostic yield of electroencephalography, computed tomography, and Doppler ultrasonography, 2% to 6%). Third, patients in whom heart disease is known or suspected or those with exertional syncope are at higher risk for adverse outcomes and should have cardiac testing, including echocardiography, stress testing. Holter monitoring, or intracardiac electrophysiologic studies, alone or in combination (diagnostic yields, 5% to 35%). Fourth, syncope in the elderly often results from polypharmacy and abnormal physiologic responses to daily events. Fifth, long-term loop electrocardiography (diagnostic yield, 25% to 35%) and tilt testing (diagnostic yield < or = 60%) are most useful in patients with recurrent syncope in whom heart disease is not suspected. Sixth, psychiatric evaluation can detect mental disorders associated with syncope in up to 25% of cases. Seventh, hospitalization may be indicated for patients at high risk for cardiac syncope (those with an abnormal electrocardiogram, organic heart disease, chest pain, history of arrhythmia, age > 70 years) or with acute neurologic signs. CONCLUSIONS: Many tests for syncope have a low diagnostic yield. A careful history, physical examination, and electrocardiography will provide a diagnosis or determine whether diagnostic testing is necessary in most patients.